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Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome (WS) is a combined immunodeficiency caused by gain-of-function mutations in the C-X-C chemokine receptor type 4 (CXCR4) gene. We characterize a unique international cohort of 66 patients, including 57 (86%) cases previously unreported, with variable clinical phenotypes. Of 17 distinct CXCR4 genetic variants within our cohort, 11 were novel pathogenic variants affecting 15 individuals (23%). All variants affect the same CXCR4 region and impair CXCR4 internalization resulting in hyperactive signaling. The median age of diagnosis in our cohort (5.5 years) indicates WHIM syndrome can commonly present in childhood, although some patients are not diagnosed until adulthood. The prevalence and mean age of recognition and/or onset of clinical manifestations within our cohort were infections 88%/1.6 years, neutropenia 98%/3.8 years, lymphopenia 88%/5.0 years, and warts 40%/12.1 years. However, we report greater prevalence and variety of autoimmune complications of WHIM syndrome (21.2%) than reported previously. Patients with versus without family history of WHIM syndrome were diagnosed earlier (22%, average age 1.3 years versus 78%, average age 5 years, respectively). Patients with a family history of WHIM syndrome also received earlier treatment, experienced less hospitalization, and had less end-organ damage. This observation reinforces previous reports that early treatment for WHIM syndrome improves outcomes. Only one patient died; death was attributed to complications of hematopoietic stem cell transplantation. The variable expressivity of WHIM syndrome in pediatric patients delays their diagnosis and therapy. Early-onset bacterial infections with severe neutropenia and/or lymphopenia should prompt genetic testing for WHIM syndrome, even in the absence of warts.

Background: WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome is a rare, autosomal-dominant primary immunodeficiency. Gain-of-function (GOF) mutations in the CXCR4 gene are the most common cause of WHIM syndrome, manifesting as panleukopenia with severe neutropenia, lymphopenia, and monocytopenia, recurrent bacterial infections, unusual susceptibility to human papillomavirus infections with intractable mucocutaneous warts, and increased risk of malignancy (McDermott DH, et al. Immunol Rev. 2019;2878:91-102). Mavorixafor is an investigational, small-molecule, selective antagonist of the CXCR4 receptor being developed as an oral, once-daily (QD) treatment for patients with WHIM syndrome (Dale DC, et al. Blood. 2020;136(26):2994-3003). Objective: We present an update on the clinical outcomes of patients with WHIM syndrome who continued in the long-term extension of the phase 2 study, highlighting long-term safety and efficacy. Methods: A long-term extension is ongoing as part of the open-label, prospective, dose-escalation, phase 2 study evaluating the safety and efficacy of mavorixafor (NCT03005327) in adults with WHIM syndrome. Individuals with a pathogenic GOF CXCR4 mutation and absolute neutrophil count ≤400/μL and/or absolute lymphocyte count ≤650/μL were included. All provided written informed consent. The primary objectives were to evaluate safety and tolerability and assess safe dosage. Exploratory efficacy end points included changes in infection rates, number of cutaneous warts, and white blood cell counts, compared to baseline. Researchers completed detailed interviews of 4 participants continuing in the study to assess their overall study experience and perceived treatment effects. Results: Five of 8 patients in the dose-finding phase 2 study entered into the long-term extension (LTE); median treatment duration was 148.4 weeks. One patient left the LTE because of study fatigue, and all 5 patients had dose escalation to 400 mg oral QD as of May 2021. As of the November 2020 data cutoff, annualized infection rates decreased from 5.6/year at study baseline to 2.2/year at 40 months' treatment, providing evidence of persistent reduction of infections over time. At doses of 300 and 400mg QD (n=7), the mean time above threshold for ANC and ALC were 12.7 hours (SD ± 9.8) and 16.9 hours (SD ± 5.9) compared to 2.1 hours (SD ± 3.3) and 11.5 hours (SD ± 5.9) at doses ≤200 mg QD, respectively. One patient experienced a 79% reduction in warts. Safety data review at May 2021 showed that there were 12 minor treatment-emergent adverse events (grade 1) with long-term treatment (46 months), no treatment-related infections of grade 3 or higher, no treatment-related serious adverse events, and no clinically significant laboratory abnormalities with mavorixafor treatment. Patient interviews revealed that all 4 LTE participants experienced good tolerability of mavorixafor and decreased frequency, severity, and duration of infections and decreased hospital/doctor visits. Three of 4 participants reported previous need for prophylactic treatment to prevent infection of minor wounds, but with mavorixafor, minor wounds healed without infection or need for prophylaxis. The mechanism of action of mavorixafor was of interest to 3 of 4 participants, who found it important that treatment address the underlying cause of disease, not simply the symptoms. Two participants reported a QOL improvement, and the other 2 reported that WHIM syndrome never affected their QOL Conclusion: Ongoing long-term treatment of adults with WHIM syndrome with mavorixafor 300 to 400mg shows durable increase in neutrophils and lymphocytes and sustained improvements in infections and warts. Detailed patient interviews for patient global impression of changes are consistent with sustained clinical benefit of long-term treatment. Mavorixafor has the potential to be a safe, effective, and long-term therapy targeting the underlying cause of WHIM syndrome. A global phase 3 registrational study is ongoing. Disclosures Dale: X4 Pharmaceuticals: Consultancy, Honoraria, Research Funding. Firkin: X4 Pharmaceuticals: Research Funding. Bolyard: X4 Pharmaceuticals: Research Funding. Tang: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Jiang: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. MacLeod: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Cadavid: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Hu: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company.

Background: WHIM (Warts, Hypogammaglobulinemia, Infections, Myelokathexis) Syndrome is a serious, ultrarare genetic disorder caused by a gain-of-function mutation in CXCR4 that causes profound neutropenia and lymphopenia associated with increased rates of bacterial and viral infections. Long-term sequelae include hearing loss, bronchiectasis, and HPV-associated malignancies. The cancer risk in WHIM patients is estimated at 30% by age 40. There is currently no treatment that addresses the underlying mechanism of disease. G-CSF increases neutrophil counts but does not appear to reduce infection rates; use of parenteral gamma globulin has had mixed reports of benefit, but no controlled trials have been reported; Plerixafor, a CXCR4 antagonist, has been shown to increase leukocyte counts and reduce infection rates when absolute neutrophil counts (ANC)>600 mm-3 and absolute lymphocyte counts (ALC)>1000 mm-3, but is a parenteral agent that must be administered twice daily. X4P-001 is an orally available, allosteric inhibitor of CXCR4 that is being developed to treat WHIM. We report here the PK/PD data from the Phase 2 portion of Phase 2/3 trial X4P-001 MKKA (NCT03005327) in WHIM patients that led to selection of the dose for Phase 3 development. Methods: Study X4P-001 MKKA is a Phase 2/3 study. The primary objective of Ph2 portion was to assess the dose required to achieve a consistent increase in circulating neutrophils and lymphocytes. Adult patients with WHIM syndrome, with documented WHIM-associated genotype, and either ANC Results: Eight patients were enrolled and were evaluable for efficacy. 6 of 8 were female, and the mean (SD) age was 35.5 (13.37). Two patients started treatment with 50 mg, then received, 100, 150, 300 and 400 mg; 2 started at 100 and then received 200 and 300 mg; 2 started at 200 mg; 1 escalated to 300 and 400 mg while the other terminated after 1 week due to an adverse event (AE). Two started at 300 mg and did not escalate. Doses of at least 300 mg/day were needed to achieve success criteria for ANC, while at doses ≥100 mg/day, 50-100% met success criteria for ALC. (Figure 1) Two patients discontinued: 1 due to an AE of grade 1 rash, and 1 voluntarily withdrew. No serious AEs were reported. One patient had unrelated cholecystitis (grade 3). All other AEs were grade 1 or 2. Conclusions: Treatment of WHIM patients with X4P-001 results in meaningful increases in ANC at doses ≥300 mg, and in ALC at doses ≥100 mg per day for at least 5 weeks. These doses are anticipated to be associated with clinically meaningful outcomes in terms of infections and warts. X4P-001 appeared to be safe and well-tolerated at doses of 50-400 mg per day.4 Disclosures Dale: Athelas, Inc.: Equity Ownership; Amgen: Consultancy, Research Funding; Sanofi-Aventi: Consultancy, Honoraria; Cellerant: Other: Scientific Advisory Board; Hospira: Consultancy; Prolong: Consultancy; Beheringer-Ingelheim: Consultancy; Coherus: Consultancy. Hartmann:Cetara: Employment; X4P Pharmaceuticals: Consultancy. Brown:Certara: Employment; X4P Pharmaceuticals: Consultancy. Ebrahim:X4Pharmaceuticals: Employment. Gorelick:X4 Pharma: Consultancy; PIN Pharma: Consultancy; Shire: Consultancy; NGN Capital: Consultancy, Other: Venture partner; IntraBio: Consultancy; Zymo Consulting Group LLC: Employment.

The characteristics of severe neutropenia with a delayed onset following administration of rituximab have been evaluated in 53 consecutively treated patients. All but one patient received rituximab for the treatment of non-Hodgkin's lymphoma. Eight episodes of grade 4 neutropenia were detected between 1 and 5 months after rituximab, when administered alone on five occasions, and on three occasions in combination with chemotherapy, where neutrophil counts had recovered prior to the development of neutropenia. In three episodes, the patients presented with sepsis. Development of neutropenia did not correlate with either the presence of detectable disease or the administration of further treatment. Neutropenia was associated with selective depletion of neutrophil precursors in all but one episode, where it was associated with generalized bone marrow hypoplasia. All episodes developed after a period of either normal or mildly depressed neutrophil counts following treatment with rituximab, and persisted for between several days and several months, before undergoing spontaneous recovery in four instances, and after administration of filgrastim in the remainder. Episodes of neutropenia were associated with disordered immune status manifested by lymphopenia and hypogammaglobulinaemia, raising the possibility that either disturbance of the balance of lymphocyte subsets or an immune dyscrasia induced by rituximab resulted in the development of this type of neutropenia.

Patients with suspected multiple myeloma should be investigated with screening tests. They may have a paraprotein in the serum, Bence-Jones protein in the urine, or both.

The treatment of acute promyelocytic leukemia has improved considerably after recognition of the effectiveness of all-trans-retinoic acid (ATRA), anthracycline-based chemotherapy, and arsenic trioxide (ATO). Here we report the use of all 3 agents in combination in an APML4 phase 2 protocol. For induction, ATO was superimposed on an ATRA and idarubicin backbone, with scheduling designed to exploit antileukemic synergy while minimizing cardiotoxicity and the severity of differentiation syndrome. Consolidation comprised 2 cycles of ATRA and ATO without chemotherapy, followed by 2 years of maintenance with ATRA, oral methotrexate, and 6-mercaptopurine. Of 124 evaluable patients, there were 4 (3.2%) early deaths, 118 (95%) hematologic complete remissions, and all 112 patients who commenced consolidation attained molecular complete remission. The 2-year rate for freedom from relapse is 97.5%, failure-free survival 88.1%, and overall survival 93.2%. These outcomes were not influenced by FLT3 mutation status, whereas failure-free survival was correlated with Sanz risk stratification (P[trend] = .03). Compared with our previously reported ATRA/idarubicin-based protocol (APML3), APML4 patients had statistically significantly improved freedom from relapse (P = .006) and failure-free survival (P = .01). In conclusion, the use of ATO in both induction and consolidation achieved excellent outcomes despite a substantial reduction in anthracycline exposure. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12605000070639.

The response of hemopoietic activity in long term culture of human bone marrow (LTMC) to exogenous c-kit ligand has been investigated. Addition of c-kit ligand as recombinant Stem Cell Factor after the adherent stromal cell layer had become confluent failed to increase the content of hemopoietic cells in the culture system. Production of hemopoietic progenitors and differentiated progeny was on the other hand amplified by addition of c-kit ligand at regular intervals from the initiation of the culture, and resulted in net formation of these cells in the culture system. The characteristics of the response were consistent with consequences of increased survival of hemopoietic progenitors during a vulnerable initial phase in which the availability of endogenous c-kit ligand was limited by the initially low number of stromal cells. The increase in differentiated progeny was essentially due to increased formation of neutrophil series, and the lack of increased basophil production under these circumstances presumably reflected the nature of the contributory effects of endogenously generated growth regulatory molecules which acted in a synergistic manner with added c-kit ligand.

BACKGROUND The combination of ATRA and anthracycline-based chemotherapy has traditionally been regarded as the gold standard for induction and consolidation in previously untreated APL patients (pts), with ATO usually reserved for relapse. Recent data in Sanz low-risk (LR) and intermediate-risk (IR) APL indicate ATRA + ATO is superior to ATRA + chemotherapy (N Engl J Med 2013), but the optimal therapy for high-risk (HiR) pts remains unclear. In an attempt to improve anti-leukemic efficacy whilst limiting reliance on anthracyclines for all risk categories of APL, the ALLG incorporated ATO into an ATRA + reduced chemotherapy backbone, and the results of an interim analysis with a median follow-up of 2 years (yr) have been published (Blood 120:1570, 2012). Herein, we report results of the protocol-specified final analysis, conducted when all surviving pts had been followed for at least 2 yr after completion of consolidation. METHODS As published, APML4 protocol treatment comprised: (i) induction with ATRA (45 mg/m2 d1-36), IDA (12 mg/m2 d2,4,6,8), ATO (0.15 mg/kg d9-36), prophylactic prednisone (1 mg/kg d1-10) and aggressive hemostatic support; (ii) consolidation with ATRA and ATO (continuous in cycle 1, intermittent in cycle 2); (iii) 2 yr oral maintenance with ATRA, 6-mercaptopurine and methotrexate. Between 2004-2009, 124 evaluable pts were accrued, and median follow-up by the censor-reversing Kaplan-Meier method in this final analysis is 4.2 yr. RESULTS Median age was 44 (3-78) yr, median white cell count was 2.4 x 109/L (0.1-85.8), and median platelet count 22 x 109/L (2-173). Risk groups were 33 LR, 67 IR, 23 HiR, 1 unknown. FLT3 mutations were present in 44%, and 11% had ≥ 2 additional cytogenetic abnormalities (2+ACA). There were 4 (3.2%) deaths during induction (myocardial infarction d1, cerebral hemorrhage d3 and d7, cerebral edema and seizures d30). Grade 3-4 non-hematological adverse events included differentiation syndrome in 14%, and frequent but reversible biochemical hepatic and gastrointestinal toxicity. Q-Tc prolongation > 500 msec occurred in 14%, but there were no cases of ventricular arrhythmias or torsades de pointe. Significant neurological and cutaneous toxicity were infrequent. After induction, 118 pts (95%) achieved hematological complete remission; 112 commenced consolidation, and all were in molecular remission after cycle 2. A total of 5 relapses and 3 deaths have occurred post-induction, but none of the deaths were attributable to protocol therapy. Severe adverse events were less common during the chemotherapy-free consolidation cycles, especially cycle 2. The frequency of grade 3-4 neutropenia was 62% in cycle 1 and 27% in cycle 2, but there was no grade 3-4 thrombocytopenia. The following table lists event-free survival (EFS), disease-free survival (DFS), overall survival (OS) and cumulative incidence of relapse (CIR): Table All pts LR IR HiR 2 yr 5 yr 2 yr 5 yr 2 yr 5 yr 2 yr 5 yr EFS 92% 90% 97% 97% 93% 89% 83% 83% DFS 97% 95% 100% 100% 97% 93% 95% 95% OS 94% 94% 97% 97% 96% 96% 87% 87% CIR 3% 5% 0% 0% 3% 7% 5% 5% In univariate analysis, 2+ACA predicted for inferior DFS (P = .04), whereas age > 70 was associated with increased risk of early death (ED, P = .02), inferior EFS (P = .0002), and inferior OS (P = .001). Neither Sanz risk category nor FLT3 mutation status was significantly correlated with these outcome endpoints (all P > .05). In multivariate analysis, the significant associations of 2+ACA (P = .04 for DFS) and age > 70 (P = .0002 for EFS, P = .005 for OS) were retained. In addition, Sanz risk category was correlated with EFS (P[trend] = .003) and OS (P[trend] = .02). When compared with our previous ALLG APML3 trial (ATRA + IDA for induction and consolidation without ATO; Haematologica 2012), treatment with APML4 was associated with substantial and statistically significant improvements (see Figure) in EFS (P = .002), DFS (P = .001) and OS (P = .02). The significance of trial assignment was retained in multivariate analysis when APML3 and APML4 data were combined. CONCLUSIONS APML4 is a potent anti-leukemic regimen with manageable toxicity and a low ED rate. EFS and OS remain impressive with mature follow-up, and were influenced primarily by advanced age and Sanz risk category. The CIR was 5%, and was only associated with 2+ACA. Our results support the inclusion of ATO in induction and consolidation as front-line therapy for APL whilst simultaneously limiting cumulative anthracycline exposure. Figure 1 Figure 1. Disclosures Off Label Use: Arsenic trioxide is currently only registered in the US, Europe and Australia for the treatment of relapsed APL. This report includes its use in the initial treatment of APL.

Summary Disseminated enteric human cytopathogenic orphan (echo) virus infection after allogeneic bone marrow transplantation has been reported once previously: a patient developed a fatal infection with the virus being isolated from brain, lung and heart. We report a second case of disseminated echovirus infection in which virus was isolated from the stomach and liver. On this occasion the infection was associated with the development of biopsy-proven acute graft-versus-host disease of the skin, stomach, colon and liver. The infection resolved without sequelae.

Summary Disseminated infection with the fungus Scedosporium inflatum in a neutropenic patient with non-Hodgkins lymphoma presented with the triad of muscle tenderness, papular skin lesions and fever, and progressed rapidly to a fatal outcome. This represents the first reported instance of fatal widely disseminated infection with this organism, and demonstrates that the triad of presenting clinical features, formerly reported to be pathognomic of systemic candidiasis, can no longer be regarded as specific for infection with a particular species of yeast or fungus.

:Neutropenia is a life-threatening sequel of hematological disorders and a dominant factor limiting the dosage of cytotoxic chemotherapy. The role of the neutrophil is of such importance in defence against microbial invasion that measures that modify the behaviour of residual hemopoietic tissue to promote a modest increase in neutrophils, can confer considerable benefit by reducing the frequency and severity of infection. Such a change can be mediated in bone marrow depression by diversion of more progeny of immature precursors into the neutrophil series, or by enhancement of the stimulatory drive operating on neutrophil production. The former effect can be achieved by hypertransfusion of red cells to reduce the demand on the limited precursor population for cells of the erythroid series. The latter effect can be achieved by administration of lithium carbonate. Neutropenia caused by autoimmune injury to the neutrophil series can also be successfully modified by measures which suppress the underlying immune dyscrasia or the function of the reticuloendothelial system. Corticosteroid administration and splenectomy can be helpful in certain specific types of neutropenia. Administration of cyclophosphamide and azathioprine has both mutagenic and marrow suppressive potential, but can induce remissions in severe chronic isolated neutropenia and in systemic lupus erythematosis.

Summary: Three cases of pure red cell aplasia (PRCA) are reported. PRCA developed with no apparent cause in the first case, was associated with histiocytic lymphoma in the second and with diphenylhydantoin therapy in the third. In vitro studies showed the presence of toxic factors against erythroid precursors in the second and third cases. It is argued that the absence of such factors in the serum of the first case does not rule out antibody-mediated damage to erythroid precursors in vivo as the demonstration in vitro would require antibody excess in vivo. Steroids induced a remission in the first two cases providing further evidence that an immunological mechanism is responsible for the PRCA. Withdrawal from diphenylhydantoin plus steroid therapy induced a rapid remission in the third case.

Summary: Very high serum muramidase concentrations in the absence of renal impairment can serve as a marker of a number of haematological neoplastic disorders, and several cases are described where the presence of these disorders was indicated by this means before the diagnosis could be established on morphological grounds. The suitability of the muramidase assay for this purpose was supported by observations that muramidase concentrations in excess of approximately five times the mean normal value were correlated closely with either chronic granulocytic, acute monocytic or myelomonocytic leukaemia, myelofibrosis or polycythaemia vera. These neoplastic disorders appeared to be effectively distinguished by this criterion from other haematological and inflammatory disorders including reactive monocytic and granulocytic states which produced lesser elevation of the muramidase concentration. On the basis of the present experience, it is suggested that estimation of the serum muramidase concentration is particularly useful in the investigation of suspected leukaemia in refractory sideroblastic anaemia, persistent monocytosis, and pancytopenic states with cellular bone marrow where the morphological picture is difficult to interpret.

Severe neutropenia due to selective loss from the bone marrow of cells of the entire neutrophil maturation sequence developed in a patient with Goodpasture's Syndrome and was associated with serious infections complicating continuous ambulatory peritoneal dialysis. Involvement of T-lymphocytes in the process affecting the neutrophil series was implicated by the relation between recovery from neutropenia and treatment with antithymocyte globulin (ATG). Azathioprine and corticosteroid administration failed to sustain recovery from neutropenia induced by ATG. It is concluded that ATG can provide a nonmyelotoxic form of therapy for pure white cell aplasia whose effectiveness is independent of responsiveness to other immunosuppressive agents.

Summary: Administration of 5-fluorocytosine in fourteen cases of invasive or systemic fungal infection was accompanied in ten by elimination of the infection. Results which particularly indicated the usefulness of the drug consisted of instances where fungal infections were eliminated following the failure of amphotericin B treatment, and in some patients whose antimicrobial defences had been compromised by immunosuppressive therapy. Success was frequently obtained in infections with Candida and Aspergillus species, as well as in penetrating ocular infections where laboratory identification of the fungus had not been made. The outcome in two cases of Cryptococcus neoformans meningitis was unsatisfactory, and this was shown in one to be due to the emergence of a resistant strain. Toxicity of a minor and reversible nature was encountered in four patients, and consisted of diarrhoea, anaemia or hepatocellular damage.

The place of cytosine arabinoside (araC) in the treatment of T-cell acute lymphoblastic leukemia was studied by measuring nucleoside transport sites and the conversion of araC to its triphosphate (araCTP) in lymphoblasts from the peripheral blood of two patients, who were then treated with araC. Equilibrium binding of 3H-nitrobenzylmercaptopurine riboside (3H-NBMPR), a specific ligand of the nucleoside transporter, gave 16,510 to 29,400 sites/cell for T-lymphoblasts on presentation or early in relapse compared with 2730 +/- 1570 sites/cell for non-T-lymphoblasts. Accumulation of araCTP from 1 microM araC was four times greater in T-cell than non-T-cell lymphoblasts. One patient was treated with araC (100 mg/m2 daily x 7 days, continuous intravenously) at the time of her first leukemic relapse and complete remission was achieved with this single agent. When this patient relapsed and developed advanced disease the T lymphoblasts showed a 75% reduction in their ability to accumulate araCTP which paralleled a reduction in 3H-NBMPR binding. The second patient achieved complete remission with araC given in low dose (15 mg twice daily by subcutaneous injection) for 21 days at the time of a localised relapse in the mediastinum and pleura. These studies suggest that araC may have a place in the therapy of early stage T-lymphoblastic disease.

Retrospective analysis of 158 cases of adult acute leukaemia: factors influencing prognosis and treatment response. E. Januszewicz, F. C. Firkin, C. N. Chesterman, O. M. Garson, W. Beswick, M. J. Keating and D. G. Penington, Aust. N.Z. J. Med., 1982, 12, pp. 238–245. Discriminant and regression analyses were employed to determine the influence of a large number of clinical and laboratory indices on outcome of treatment in a series of 158 adults presenting with acute leukaemia between 1970 and 1977. Induction therapy had been most commonly cytosine arabinoside plus daunorubicin, vincristine and prednisolone. This induced complete remission in 42% of non-lymphoblastic, and in 58% of lymphoblastic plus undifferentiated leukaemias. Some induction failures who had non-lymphoblastic leukaemia were treated with cytosine arabinoside plus 6-thioguanine, which induced remissions in 46%. Advanced age was the factor most strongly associated with failure either to achieve or to sustain complete remission. Thrombocytopenia, promyelocytic leukaemia, high percentage of marrow blasts, and absence of metaphases in marrow cytogenetic preparations were also associated with poor survival. A number of other factors which appeared to be associated with poor prognosis were found by the analysis to lack significance as independent variables.

The influence of material released by activated human platelets on the phagocytic activity of human neutrophils and monocytes has been investigated under conditions where there was a low background level of exposure of the leukocytes to platelet release products (PRPr). Incubation with PRPr prepared from 400 X 10(9)/l platelets resulted in an approximate 3-fold increase in the proportion of leukocytes which ingested particles. Stimulation was produced by dilutions of PRPr down to 1:4 to indicate that phagocytic activity was affected by material released by concentrations of platelets within the physiological range. This response appeared to reflect stimulation of the overall phagocytic capability of the leukocytes as equivalent ingestion was observed with particles which possessed or lacked the capacity to bind complement to their surface. Enhancement of phagocytic activity was evidently secondary to induction of a change in leukocyte behaviour which was sustained in the absence of continued exposure to preparations of PRPr. These observations extend the range of human biological processes known to be responsive to PRPr, and have implications for the assessment of leukocyte phagocytic activity in vitro as this particular property could be modified by contact with PRPr during the isolation of leukocytes from peripheral blood.

Summary: A patient with a lifelong bleeding diathesis is described. Studies of haemostatic function revealed a prolonged bleeding time and reduced glass bead adhesiveness. All other routine studies of haemostatic function yielded normal results, in particular the Factor VIII level, estimated both by antibody and coagulation techniques. Ristocetininduced platelet aggregation was absent and could be corrected by the addition of plasma or serum from normal controls or haemophiliacs, but not from patients with Von Willebrand's disease. It is apparent that the Von Willebrand plasma factor is either reduced in amount or inactive in this patient without an accompanying reduction in the Factor VIII level. It is postulated that Factor VIII may have two separate sites of biological activity, one concerned with the intrinsic pathway of coagulation and the other with platelet glass bead adhesiveness and skin bleeding time. It is proposed that this patient possesses a specific abnormality in the latter site, in contradistinction to the specific defect in the site concerned with intrinsic coagulant function in haemophilia.

Serum lysozyme concentrations were assayed in a variety of haemopoietic disorders. Abnormal lysozyme levels were found to be associated with disorders of specific haemopoietic cell lines, and the investigation was directed particularly toward evaluating the usefulness of the enzyme level in the diagnosis of marrow dyscrasias where diagnosis on morphological grounds was in doubt, such as in the 'preleukaemic' state. Chronic myeloid leukaemia and myelofibrosis were both found to be associated with elevated serum lysozyme levels (30-120 μg./ml.). This occurred in myelofibrosis despite peripheral pancytopenia, suggesting that ineffective myelopoiesis might occur in this condition. Cytologically distinct myelomonocytic leukaemias were associated with high levels of lysozyme (164-180 μg./ml.); however, several cases of acute leukaemia with predominantly myeloblastic or promyelocytic features had significantly elevated levels. Therefore leukaemias with increased lysozyme were not restricted to one morphological category. Enzyme levels in these patients accurately reflected the response of the leukaemic marrow infiltration to therapy and provided a more reliable index of progress than peripheral blood examination. Monocytosis in bacterial infections produced marginally elevated lysozyme levels which were thus considerably lower than in leukaemic states. Despite the marked monocytosis in infectious mononucleosis the level was less than in bacterial infections. The assay was of value in certain cases of marrow dyscrasia as an early index of leukaemic transformation. While enzyme levels were normal in uncomplicated refractory sideroblastic anaemia, in 3 cases elevated serum lysozyme heralded the onset of overt myelomonocytic leukaemia or a myeloproliferative disorder with a leukaemoid peripheral blood picture.