Search

Background Late sequelae of COVID-19 have been reported; however, few studies have investigated the time course or incidence of late new COVID-19–related health conditions (post-COVID conditions) after COVID-19 diagnosis. Studies distinguishing post-COVID conditions from late conditions caused by other etiologies are lacking. Using data from a large administrative all-payer database, we assessed type, association, and timing of post-COVID conditions following COVID-19 diagnosis. Methods Using the Premier Healthcare Database Special COVID-19 Release (release date, 20 October 2020) data, during March–June 2020, 27 589 inpatients and 46 857 outpatients diagnosed with COVID-19 (case-patients) were 1:1 matched with patients without COVID-19 through the 4-month follow-up period (control-patients) by using propensity score matching. In this matched-cohort study, adjusted ORs were calculated to assess for late conditions that were more common in case-patients than control-patients. Incidence proportion was calculated for conditions that were more common in case-patients than control-patients during 31–120 days following a COVID-19 encounter. Results During 31–120 days after an initial COVID-19 inpatient hospitalization, 7.0% of adults experienced ≥1 of 5 post-COVID conditions. Among adult outpatients with COVID-19, 7.7% experienced ≥1 of 10 post-COVID conditions. During 31–60 days after an initial outpatient encounter, adults with COVID-19 were 2.8 times as likely to experience acute pulmonary embolism as outpatient control-patients and also more likely to experience a range of conditions affecting multiple body systems (eg, nonspecific chest pain, fatigue, headache, and respiratory, nervous, circulatory, and gastrointestinal symptoms) than outpatient control-patients. Conclusions These findings add to the evidence of late health conditions possibly related to COVID-19 in adults following COVID-19 diagnosis and can inform healthcare practice and resource planning for follow-up COVID-19 care.

Species in the brackish and estuarine ecosystems will experience multiple changes in hydrographic variables due to ongoing climate change and nutrient loads. Here, we investigate how a glacial relict species (Saduria entomon), having relatively cold, low salinity biogeographic origin, could be affected by the combined scenarios of climate change and eutrophication. It is an important prey for higher trophic-level species such as cod, and a predator of other benthic animals. We constructed habitat distribution models based occurrence and density of this species across the entire Baltic and estimated the relative importance of different driving variables. We then used two regional coupled ocean-biogeochemical models to investigate the combined impacts of two future climate change and nutrient loads scenarios on its spatial distribution in 2070–2100. According to the scenarios, the Baltic Sea will become warmer and fresher. Our results show that expected changes in salinity and temperature outrank those due to two nutrient-load scenarios (Baltic Sea Action Plan and business as usual) in their effect on S. entomon distribution. The results are relatively similar when using different models with the same scenarios, thereby increasing the confidence of projections. Overall, our models predict a net increase (and local declines) of suitable habitat area, total abundance and biomass for this species, which is probably facilitated by strong osmoregulation ability and tolerance to temperature changes. We emphasize the necessity of considering multiple hydrographic variables when estimating climate change impacts on species living in brackish and estuarine systems.

JQ1 is a small-molecule inhibitor of the bromodomain and extra terminal (BET) protein family that potently inhibits the bromodomain testis-specific protein (BRDT), which is essential for spermatogenesis. JQ1 treatment produces a reversible contraceptive effect by targeting the activity of BRDT in mouse male germ cells, validating BRDT as a male contraceptive target. Although JQ1 possesses favourable physical properties, it exhibits a short half-life. Because the details of xenobiotic metabolism play important roles in the optimization of drug candidates and in determining the role of metabolism in drug efficacy, we investigated the metabolism of JQ1 in human and mouse liver microsomes. We present the first comprehensive view of JQ1 metabolism in liver microsomes, distinguishing nine JQ1 metabolites, including three monohydroxylated, one de-tert-butylated, two dihydroxylated, one monohydroxylated/dehydrogenated, one monohydroxylated-de-tert-butylated and one dihydroxylated/dehydrogenated variant of JQ1. The dominant metabolite (M1) in both human and mouse liver microsomes is monohydroxylated on the fused three-ring core. Using recombinant cytochrome P450 (CYP) enzymes, chemical inhibitors and the liver S9 fraction of Cyp3a-null mice, we identify enzymes that contribute to the formation of these metabolites. Cytochrome P450 family 3 subfamily A member 4 (CYP3A4) is the main contributor to the production of JQ1 metabolites in vitro, and the CYP3A4/5 inhibitor ketoconazole strongly inhibits JQ1 metabolism in both human and mouse liver microsomes. Our findings suggest that JQ1 half-life and efficacy might be improved in vivo by co-administration of a selective CYP inhibitor, thereby impacting the use of JQ1 as a probe for BRDT activity in spermatogenesis and as a probe or therapeutic in other systems., Nine JQ1 metabolites were identified and characterized in liver microsomes, and the enzyme CYP3A4 mediates the formation of most JQ1 metabolites.

Introduction Right heart catheterisation (RHC) is the gold standard investigation for the diagnosis of pulmonary hypertension (PH). Transthoracic echocardiography (TTE) allows non-invasive screening for PH. This retrospective audit sought to compare the accuracy of non-invasive Doppler estimates of pulmonary artery pressure and pulmonary vascular resistance (PVR) compared to RHC in a real world cohort referred to a shared care PH centre. Method Between 2010 and 2019, a total of 310 patients referred for initial assessment of PH underwent TTE followed by RHC (mean interval 31±30 days). Bland-Altman analysis was used to retrospectively investigate the accuracy of Doppler estimates of Pulmonary Artery Systolic Pressure (PASP), mean Pulmonary Artery Pressure (mPAP), Right Atrial Pressure (RAP) and PVR compared to RHC. TTE mPAP estimates were made using the pulmonary regurgitation velocity at the beginning of diastole (mPAP = 4(PRVBD)2 + RAP). TTE PVR estimates were calculated using the equation 10(TRV / RVOTVTI) + 0.16. Results Seventy-six percent of the cohort (n=235) had RHC diagnosed PH (average mPAP 42.8±11.7mmHg). The peak tricuspid regurgitation velocity (TRV) was measurable in 87% (n=269) and was unmeasurable in 8% (n=19) of those with confirmed RHC PH. Ten percent (n=30) had inadequate IVC imaging. TTE estimates of PASP (n=239) had a good correlation to RHC PASP (rs=0.82, 95% CI 0.75–0.84). TTE PASP estimates tended to underestimate RHC PASP (bias −3.7±15.2mmHg) with wide limits of agreement (95% limits of agreement −33.5–26.1mmHg) (figure 1); highlighting the imprecision of Doppler estimates alone. Only 44% of TTE PASP estimates were within 10mmHg of RHC PASP readings. Underestimation occurred more frequently accounting for 66% of inaccurate TTE PASP estimates. TTE RAP estimates (n=292) were weakly correlated to RHC RAP (rs=0.38, 95% CI 0.27–0.48). TTE estimates of mPAP were only measurable in 81 patients and demonstrated moderate correlation to RHC mPAP (rs=0.58, 95% CI 0.4–0.71). TTE estimates tended to underestimate RHC mPAP (bias of −10±10.9mmHg) with wide limits of agreement (95% limits of agreement −31.3–11.3mmHg) (figure 1) suggesting poor accuracy and precision. Only 51% of TTE estimates were within 10mmHg of RHC mPAP with 93% of inaccuracies due to an underestimation of RHC mPAP. TTE PVR estimates (n=238) correlated well with RHC PVR measures (rs=0.68, 95% CI 0.6–0.74). However, Bland-Altman analysis (figure 2) demonstrated bias of −2.2±3.1WU with wide limits of agreement (95% limits of agreement −8.2–3.8WU), highlighting significant inaccuracy. Conclusion Doppler TTE measures to assess PH lack accuracy when compared with the gold standard RHC. Furthermore, the peak TRV was unmeasurable in 8% of those with confirmed RHC diagnosed PH. These findings further support the use of a multi parameter TTE approach for screening of PH. Funding Acknowledgement Type of funding sources: None.

Historical marine ecology has shown that many exploited animal populations declined before their abundance was quantified by scientists. This situation applies for autumn-spawning herring (Clupea harengus) in the Baltic Sea. This stock used to be the dominant spawning group of herring in the early decades of the 1900s and supported several commercially important fisheries, including in the Gulf of Riga (GoR). However, the GoR stock declined during the 1960–1970s and has not recovered. Neither the former biomass nor reasons for its decline are known. Here, we recover and analyse historical fishery and biological data and conduct population development simulations to evaluate the hypothesis that exploitation may have been sufficient to lead the stock towards commercial extinction. We found that the estimated exploitation pattern, including exploitation of juveniles, was unsustainable and led to stock decline. The pattern of exploitation of this stock was consistent with that which caused collapses of other herring stocks, which have since recovered. If autumn-spawning herring in the GoR recovers, our findings indicate that this stock could support sustainable annual yields of ∼4000 t and diversify the fishery resource base, which is presently restricted to a relatively small number of species for essentially local coastal inhabitants.

Projections of the impacts of climate change on marine ecosystems are a key prerequisite for the planning of adaptation strategies, yet they are inevitably associated with uncertainty. Identifying, quantifying, and communicating this uncertainty is key to both evaluating the risk associated with a projection and building confidence in its robustness. We review how uncertainties in such projections are handled in marine science. We employ an approach developed in climate modelling by breaking uncertainty down into (i) structural (model) uncertainty, (ii) initialization and internal variability uncertainty, (iii) parametric uncertainty, and (iv) scenario uncertainty. For each uncertainty type, we then examine the current state-of-the-art in assessing and quantifying its relative importance. We consider whether the marine scientific community has addressed these types of uncertainty sufficiently and highlight the opportunities and challenges associated with doing a better job. We find that even within a relatively small field such as marine science, there are substantial differences between subdisciplines in the degree of attention given to each type of uncertainty. We find that initialization uncertainty is rarely treated explicitly and reducing this type of uncertainty may deliver gains on the seasonal-to-decadal time-scale. We conclude that all parts of marine science could benefit from a greater exchange of ideas, particularly concerning such a universal problem such as the treatment of uncertainty. Finally, marine science should strive to reach the point where scenario uncertainty is the dominant uncertainty in our projections.

Procalcitonin (PCT) has been shown to be a useful surrogate marker in identifying patients with various bacterial infections. PCT has been studied as a diagnostic marker in differentiating bacterial pneumonia from other respiratory conditions such as chronic obstructive pulmonary disease exacerbations or viral pneumonia. Differentiating bacterial from nonbacterial pneumonia using PCT has shown to reduce antibiotic usage, length of stay, and antibiotic-related adverse effects. PCT has also been studied in patients with sepsis in an effort to reduce unnecessary antibiotic usage and decrease the length of antibiotic therapy. This article focuses on the use of PCT in patients with various degrees of chronic kidney disease in addition to various forms of dialysis, as chronic kidney disease may alter baseline levels of PCT and thus result in inappropriate use of PCT in this population.

Hollowed, A. B., Barange, M., Beamish, R., Brander, K., Cochrane, K., Drinkwater, K., Foreman, M., Hare, J., Holt, J., Ito, S-I., Kim, S., King, J., Loeng, H., MacKenzie, B., Mueter, F., Okey, T., Peck, M. A., Radchenko, V., Rice, J., Schirripa, M., Yatsu, A., and Yamanaka, Y. 2013. Projected impacts of climate change on marine fish and fisheries. – ICES Journal of Marine Science, 70: 1023–1037. This paper reviews current literature on the projected effects of climate change on marine fish and shellfish, their fisheries, and fishery-dependent communities throughout the northern hemisphere. The review addresses the following issues: (i) expected impacts on ecosystem productivity and habitat quantity and quality; (ii) impacts of changes in production and habitat on marine fish and shellfish species including effects on the community species composition, spatial distributions, interactions, and vital rates of fish and shellfish; (iii) impacts on fisheries and their associated communities; (iv) implications for food security and associated changes; and (v) uncertainty and modelling skill assessment. Climate change will impact fish and shellfish, their fisheries, and fishery-dependent communities through a complex suite of linked processes. Integrated interdisciplinary research teams are forming in many regions to project these complex responses. National and international marine research organizations serve a key role in the coordination and integration of research to accelerate the production of projections of the effects of climate change on marine ecosystems and to move towards a future where relative impacts by region could be compared on a hemispheric or global level. Eight research foci were identified that will improve the projections of climate impacts on fish, fisheries, and fishery-dependent communities.

As a discipline, marine historical ecology (MHE) has contributed significantly to our understanding of the past state of the marine environment when levels of human impact were often very different from those today. What is less widely known is that insights from MHE have made headway into being applied within the context of present-day and long-term management and policy. This study draws attention to the applied value of MHE. We demonstrate that a broad knowledge base exists with potential for management application and advice, including the development of baselines and reference levels. Using a number of case studies from around the world, we showcase the value of historical ecology in understanding change and emphasize how it either has already informed management or has the potential to do so soon. We discuss these case studies in a context of the science–policy interface around six themes that are frequently targeted by current marine and maritime policies: climate change, biodiversity conservation, ecosystem structure, habitat integrity, food security, and human governance. We encourage science–policy bodies to actively engage with contributions from MHE, as well-informed policy decisions need to be framed within the context of historical reference points and past resource or ecosystem changes.

When panned with a transient heat denaturation approach against target enzymes, a human V(H) (antibody heavy chain variable domain) phage display library yielded V(H)s with composite characteristics of binding, non-aggregation and reversible thermal unfolding. Moreover, selection was characterized by enrichment for V(H)s with (i) an even number of disulfide forming Cys residues in complementarity-determining region (CDR) 1 and CDR3 and (ii) acidic isoelectric points. This parallels naturally occurring camelid and shark single-domain antibodies (sdAbs) which are also characterized by (i) solubility and reversible unfolding, (ii) a high occurrence of disulfide forming Cys in their CDRs, particularly, in CDR1 and CDR3 and (iii) acidic V(H)s as inferred here by a pI distribution analysis, reported here, of pools of human and camelid V(H) and V(H)H (camelid heavy chain antibody V(H)) sequences. Our results, reinforced by previous observations by others, suggest that protein acidification may yet be another mechanism nature has devised to create functional sdAbs and that this concept along with the inclusion of inter-CDR disulfide linkages may be applied to human V(H) domains/libraries for non-aggregation optimization. In addition, calculation of theoretical pIs of V(H)s selected by panning may be used for rapid and precise identification of non-aggregating V(H)s.

Background: A review of the activities of the Grampian travel clinic was carried out over 1 year to obtain an overall perspective of the clinic workload and to determine how much of the workload was dependent on the oil industry. Methods: A specially designed data collection sheet was completed for each of the 669 consultations conducted at the Grampian travel clinic, Aberdeen, between February 1, 2002, and January 31, 2003. Results: Patients attending the clinic came in equal numbers from the city of Aberdeen and the Grampian region. Twenty-five percent were traveling for work purposes: 87.4% of this travel was oil related, and most patients were headed to Africa. The commonest vaccines given were for yellow fever, Japanese B encephalitis, and rabies, reflecting the specialist nature of the clinic. Most travelers did leave adequate time for immunization before travel. The public is still apprehensive about using mefloquine as malarial prophylaxis. Conclusions: Most attendees were traveling on holiday, but a quarter of the consultations were for travel related to the oil industry. Almost 70% of attendees had already visited their general practitioner and were therefore attending the clinic for specialist advice and vaccines. There is a need for increased clinic capacity.

Indoleamine 2,3-dioxygenase (IDO) has been implicated in regulation of feto-maternal tolerance and protection against intracellular and extracellular pathogens. We have studied the expression of IDO in the human female reproductive tract and the placenta by immunohistochemistry. Endometrial glandular and surface epithelial cells showed increasing IDO expression during the course of the menstrual cycle. In term placenta, IDO was irregularly localized to the mesenchymal core and found in isolated areas of the syncytiotrophoblast. In first trimester pregnancy, IDO was not present in placental villi, but was present in glandular epithelium of the decidua, and there were distinctly positive cells scattered in the connective tissue, sometimes in conjunction with lymphoid aggregates. The endothelium of spiral arteries and of capillaries showed some, albeit no generalized, reactivity. IDO was also present in the epithelium of cervical glands and of Fallopian tubes. Specificity of antibody binding was confirmed by Western blot analysis. IDO mRNA was detected in first trimester decidua as determined by RT-PCR. IDO is secreted, as determined by analysis of cervical mucus by high pressure liquid chromatography for the presence of the tryptophan metabolite L-kynurenine, indicating IDO activity. Our results support the concept of IDO providing a mechanism of innate immunity protecting against ascending infections in the female reproductive tract.

Neonatal sepsis is most often caused by group B streptococci (GBS) and is a major cause of death in the neonatal period. The response of the immune system in the newborn child has received much attention and is thought to be deficient in a number of ways. The effector response of neonatal monocyte-derived macrophages (MDM) was investigated. Interferon-gamma induced the activation of indoleamine 2,3-dioxygenase in MDM and inhibited the growth of GBS. Both effects were enhanced by the addition of tumor necrosis factor-alpha to the culture conditions. The coincident supplementation of L-tryptophan with the bacteria abrogated the bacterial growth inhibition, thus confirming the causative role of L-tryptophan depletion. Control of the extracellular as well as intracellular L-tryptophan levels may thus be one of the effector mechanisms with which the immune system defends the host against GBS dissemination and disease.

Factors involved in trap design, trap construction, and trapping protocol in the field were examined to determine their influence on accuracy of an established monitoring program for the carrot rust fly, Psila rosae (F.). Changing the adhesive from Stikem Special to Stiky Stuff did not alter trap efficacy significantly. Catches of P. rosae decreased linearly with decreased trap surface area, but reducing coverage of standard-sized traps coated with adhesive by up to 75% did not alter trap efficacy significantly. Lengthening trap inspections from 4 d to 7 or 10 d would have underestimated counts of flies on traps, leading to omissions or delays in spray recommendations. Traps situated near outer perimeters of fields generally captured more flies than traps placed inside fields. This trend was sometimes reversed when crops were young, and catches were equal on inner versus outer traps in a mature field late in the growing season. Traps placed at corners of fields generally captured more flies than those placed between corner traps along field perimeters. Traps coated on both north- and south-facing surfaces captured significantly more flies on the north face in all three flight periods. Based on the results, a modified monitoring program for P. rosae is described that would be as effective, but more economical to operate than the existing program in British Columbia.

It has been suggested recently that the two most widely used reference strains of Candida albicans (NCPF 3153 and B311) were derived from the same parental strain. However, records maintained at the PHLS Mycological Reference Laboratory suggest otherwise. In an attempt to resolve this contradiction, assessments were made of biotypes, resistogram patterns, morphotypes and restriction fragment length polymorphisms (RFLP) for nine isolates of NCPF 3153 and six of B311, obtained from 11 different centres. Biotyping results showed that with one exception (isolate No. 3, putatively derived from NCPF 3153), only strains derived from B311 were resistant to flucytosine at 12.5 micrograms ml-1 in agar. Moreover, strain No. 3 differed from other NCPF 3153 derivatives in its resistogram and RFLP patterns, which were indistinguishable from B311 isolates. It was concluded that the two reference strains were not derived from the same parental strain, and that they could be distinguished from each other by biotype, resistogram and RFLP patterns. Strains designated as B311 resembled each other closely, in contrast to NCPF 3153 isolates, which had variable resistogram and RFLP patterns. The simplest screening procedure for distinguishing B311 isolates was their resistance to flucytosine. Since test isolate No. 3 differed consistently from other putative NCPF 3153 isolates, it was concluded that its status was uncertain and that its designation as = NCPF 3153 should be discontinued.

A radial "high-performance" thin-layer chromatographic (HPTLC) method is described by which the percentages and ratios of phosphatidylinositol, sphingomyelin, lecithin, phosphatidylethanolamine, phosphatidylglycerol, and dimethyl phosphatidylethanolamine may be determined simultaneously. An additional method for radial HPTLC determination of saturated phosphatidylcholine is described. We report results of application of these methods to greater than 2000 specimens of amniotic fluid from both diabetic and nondiabetic cases.

Background Hypercholesterolaemia is a recognized risk factor for the development of arteriosclerosis. There is compelling evidence to support the use of lipid-lowering strategies in all hypercholesterolaemic patients with arteriosclerotic disease. In peripheral arterial disease (PAD), national guidelines recommend treatment if total cholesterol exceeds 5·0 mmol l−1. The prevalence of hypercholesterolaemia in patients with PAD was determined and the adequacy of lipid management before vascular referral was examined. Methods This was a prospective study of 233 consecutive patients admitted electively to this vascular surgery unit between December 1997 and December 1998. Some 68 patients were admitted with carotid disease, 81 with an aneurysm and 84 with intermittent claudication. A fasting venous blood sample was obtained from each patient. Results There were 175 men and 58 women, of median age 67 (range 37–85) and 68 (range 47–85) years respectively. Only 35 patients (15 per cent) were previously known to be hypercholesterolaemic; all but one were receiving treatment (one dietary, 33 statin). Of the remaining 198 patients, 124 (63 per cent) had a serum cholesterol level above 5·0 mmol l−1. A further 17 patients (9 per cent) had total cholesterol/high-density lipoprotein: cholesterol ratio greater than 5·0; these patients may also benefit from lipid-lowering therapy. In total, 141 (80 per cent) of 176 hypercholesterolaemic patients were undiagnosed at the time of hospital admission. Conclusion Hypercholesterolaemia is an important and correctable risk factor found in the majority of patients with PAD, but despite national guidelines and clear evidence from randomized controlled trials it is simply not being diagnosed in primary care. All elective patients with PAD should be screened for hypercholesterolaemia during their admission.

Physical processes are recognized as being important in producing, aggregating, and dispersing food organisms required by various stages of important fish species (e.g. cod, mackerel, etc.). There is at present a gap in the knowledge of how these processes, which take place at intermediate scales (tens of metres to kilometres in the horizontal, several metres in the vertical, and hours to a few days in time) affect fish biology, including recruitment. Examples of intermediate-scale physical processes include tidal fronts, shelf-break fronts, upwelling filaments, Langmuir cells and thermoclines. These types of features represent a research opportunity for studies involving new field and theoretical investigations, as well as retrospective data analyses (ICES/GLOBEC, 1994). At Theme Session Q of the 1995 ICES Annual Science Conference held in Aalborg, Denmark, entitled ‘‘Intermediate-Scale Processes and Their Influence on the Transport and Food Environment of Fish’’, 22 papers dealing with this subject were presented. From the presentations and subsequent discussions, the following points emerged

Plots of transplanted cauliflower were assessed over a 3-year period to determine the effects of insecticide on the cabbage maggot, Hylemya brassicae (Weidemann); the small carabid beetle, Bembidion lampros Herbst and the staphylinid parasite, Aleochara bilineata Gyllenhal. B. lampros was the main species taken in pit-traps, and its numbers were unaffected by applications of granular chlorfenvinphos. Untreated plants averaged 7.7, 12.2 and 12.6 puparia in 1976, 1977 and 1978 respectively, of which 30.8, 42.6 and 62.2 percent were parasitized by A. billineata . Treated plants had fewer puparia with lesser percentage parasitism. Bioassays with granular insecticides in soil showed that B. lampros was quite tolerant to chlorfenvinphos, somewhat susceptible to carbofuran and isofenphos and very susceptible to terbufos.

SUMMARY.— A study of 86 infants aged 2 to 9 months who had sehorrhoeic eczema, and a similar number of clinically unaffected controls, matched for age and sex, shows that for each of 8 external areas of the skin surface the incidence of C. albicans was significantly higher among the infants with the skin disease (the differences ranged from about 8 to 39%). This conclusion was also true when only clinically affected areas of the skin surface were considered but more data are required to discover whether, as is suggested by some of the present data, a similar conclusion is justified when only clinically unaffected areas of the skin surface, of children clinically affected elsewhere, are considered. Of the infants studied, 69% of those with seborrhoeic eczema were infected with C. albicans at one or more areas of the skin surface (including the buccal mucous membrane) compared with 38% of those who had no clinical skin disease. Attention is drawn to the high incidence of C. albicans on the buccal mucous membrane of clinically unaffected infants (31·4% were so infected) and to the fact that the majority of infants infected with C. albicans had the organism either on that site, the margin of the anus, or on both. The implications of these findings for future studies of the nature of the association between C. albicans and lesions of seborrhoeic eczema are emphasized.

Bone marrow mononuclear cell populations were studied in 35 patients without myeloma, 39 patients with multiple myeloma, and 15 patients with benign monoclonal gammopathy. Bone marrow mononuclear cell receptors, responses to mitogens or allogeneic stimuli, and suppressive effects on in vitro peripheral blood lymphocyte (PBL) function were studied. In bone marrow cell populations from patients with untreated multiple myeloma, the percent of complement receptor-bearing cells and the pokeweed mitogen- and concanavalin A-stimulated responses were significantly greater than were those in bone marrow cell populations from patients without myeloma. Sheep red blood cell receptor-bearing cells were significantly greater in marrow populations from treated multiple myeloma patients compared to those from untreated multiple myeloma patients. Sheep red blood cell receptor-bearing cells from the bone marrow of multiple myeloma patients suppressed responses of the multiple myeloma patients' PBL's to autologous mitomycin C-treated bone marrow plasma cells and to allogeneic stimuli in one-way mixed leukocyte culture. Complement receptor-bearing cells suppressed the response to pokeweed mitogen. The presence of lymphocytes in the marrow compartment that are capable of suppressing the response of myeloma patients' PBL's to plasma cell antigens may be significant in the pathogenesis of multiple myeloma.