Search

The number of renal transplant recipients is increasing steadily. Physicians from all specialties are ever more likely to encounter this vulnerable group of patients. They constitute a susceptible group because of increased mortality and morbidity. Half of the renal transplants are lost due to chronic transplant failure. The primary cause of chronic transplant failure is chronic allograft nephropathy. Other causes of transplant failure are calcineurin inhibitor toxicity, recurrence of the original renal disease such as glomerulonephritis and diabetes mellitus, stenosis of the renal artery in the transplant, and urological complications. The other half of the renal transplants are lost due to the death of the recipient. The primary cause of death is cardiovascular disease due to former chronic renal, hypertension and dyslipidemia following the use of immunosuppressants. In addition malignancies, infections and bone abnormalities do occur more frequently as compared to the normal populations. Alertness is warranted following kidney transplantation by both the patients themselves as well as all the treating specialists. Careful periodical monitoring for life is required because of the risk of the abovementioned complications.

T cells play a central role in the control of and the protection against viral infections. The T cell population consists ofa diversity ofvirus-specific memory T cells. The characteristics of these T cells seem to depend largely on the type of virus for which they are specific. T cells directed against latent viruses, such as cytomegalovirus, are cytotoxic cells. T cells directed against viruses that after the initial infection are completely removed by the immune system, such as the influenza virus, are non-cytotoxic cells. The development of new immunological techniques, such as the detection of virus-specific cells with HLA-peptide tetrameric complexes, enables the characterization of the properties of virus-specific T cells in the blood and organs.

Respiratory manifestations of systemic lupus erythematosus (SLE) are frequent. The 'shrinking lung syndrome' (SLS) represents a rare complication of SLE. The pathogenesis and therapy of the SLS remains controversial. We report a series of five consecutive cases with the SLS of which we provide a detailed description of the extent and dynamics of the response to corticosteroid therapy.

During the past 30 years, solid organ transplantation has developed into a routine medical procedure. Currently, one-year transplant survival rates for kidney, heart, liver and pancreas are between 80 and 90%; for most organs, the long-term results are fair with 5-year survival rates of 60%. Inclusion criteria for potential recipients have become less stringent. These days, potential recipients are rarely excluded on the basis of their calendar age alone. The development of more and stronger immunosuppressive drugs has facilitated transplantation across wider immunological differences between donor and recipient with good results. While the number of patients on the waiting lists for organ transplantation increased, the number of organs offered for donation decreased. This has resulted in waiting times of several years for most organ transplantations. While the short-term outcome has improved significantly over the past decades, the long-term outcome has not. Most renal transplants, for example, are lost due to chronic rejection. The challenge for the future will be to improve the long-term outcome of organ transplantation and to decrease the morbidity associated with chronic immunosuppressive therapy.

Immunosuppressive drugs are agents capable of modulating at least one type of immune response in vivo at doses with tolerable side-effects. Classical immunosuppressive drugs include corticosteroids, azathioprine, cyclophosphamide, methotrexate and cyclosporine. In the past two years tacrolimus and mycophenolate mofetil were registered as immunosuppressive drugs. Tacrolimus interferes with the calcium-dependent signal transduction of T-lymphocytes. Mycophenolate mofetil is an inhibitor of purine synthesis by inhibition of the enzyme inosine monophosphate dehydrogenase. Both tacrolimus and mycophenolate mofetil have proven efficacy in both prevention and treatment of acute allograft rejection. The new drugs are stronger than the classical ones but do not cause more adverse reactions. The value in clinical medicine of some new, promising immunosuppressive drugs, i.e. sirolimus (rapamycin), mizoribine, brequinar and leflunomide remains to be proven.

Fundamental immunology has seen a tremendous development in the past decades. This has resulted in a large body of knowledge, part of which has led to applications in laboratory diagnosis, but of which little has made its way to the clinic in terms of new therapies. The progress in understanding pathogenesis of diseases is also slow. This journal is planning a series of articles that highlight the recent achievements of immunology and their consequences for understanding and treating disease.

OKT3 induces a systemic release of cytokines and a profound peripheral lymphocytopenia. In vitro, tumor necrosis factor-alpha, interleukin-1, and interferon-gamma increase adhesion molecule expression on vascular endothelium. To investigate the effects of OKT3 induced cytokine release on endothelial- and lymphocyte adhesion molecule expression in vivo, we studied sequential skin biopsies of six renal allograft recipients treated for acute rejection with 5 mg OKT3. An additional group of six patients treated for acute rejection with 50 mg methylprednisolone served as a control group. Compared to pre-treatment biopsies, biopsies taken 4.5- and 24 hours after the first OKT3 dose showed a maximal increase in VCAM-1 and ICAM-1 expression, respectively. In parallel, an increased number of CD2+, CD11a+, and CD49d+ mononuclear cells in the skin was observed in all OKT3 treated patients. No changes were observed after methylprednisolone treatment. We conclude that the OKT3 induced cytokine release induces increased ICAM-1- and VCAM-1 expression on vascular endothelium, leading to increased influx of CD2+ lymphocytes which may contribute to the peripheral lymphocytopenia after OKT3.

The aim of the present study was to analyze whether acquired transplantation tolerance had developed in patients with a long-term surviving renal or liver allograft. Analysis of antidonor cytotoxic T cell precursor frequencies was performed in 31 renal allograft recipients and 9 liver allograft recipients with good graft function 2 years after transplantation. The results demonstrated that, before transplantation, normal antidonor T cell responses were generated in both groups of patients. Two years after transplantation, donor-specific CTL nonresponsiveness had developed in a minority of the renal transplant recipients. In contrast, 8 out of 9 liver transplant recipients showed donor-specific mixed lymphocyte culture and CTL nonresponsiveness. These findings indicate that development of donor-specific T cell nonresponsiveness is not a common event after kidney transplantation, whereas liver transplantation seems to induce, at least in vitro, a state of donor-specific T cell nonresponsiveness.

The effects of the administration of OKT3, a second immunoglobulin G2a (IgG2a) anti-CD3 monoclonal antibody (mAb), and its isotype switch variant IgA on granulocyte kinetics were compared for 5 hours after the first administration of the mAb. In addition, in vivo and in vitro studies were performed on alterations in expression of CD11b and CD62L induced by these mAbs. Within 15 minutes after administration OKT3 and IgG2a anti-CD3 mAbs induced a significant decrease in circulating granulocytes, whereas IgA anti-CD3 mAb did not. Apparently the initial decrease in circulating granulocytes depends on the heavy chain of the administered anti-CD3 mAb, resulting in immunocytoadherence and sequestration in the lungs. Increased adherence to pulmonary endothelium by altered expression of CD11b and CD62L plays a minor role in this first granulocytopenia, because each mAb exerted the same effects on these adhesion molecules in vitro. The second decrease in granulocyte counts occurred 60 minutes after administration of each mAb and correlated with a significant increase in expression of CD11b and CD62L in vivo and with upregulation of CD11b and down-regulation of CD62L in vitro. These alterations could be related to the presence of tumor necrosis factor-alpha both in vivo and in vitro. Thus granulocyte kinetics from 30 minutes after administration of each anti-CD3 mAb resemble neutrophil kinetics induced by TNF-alpha.

Immunosuppressive drugs are agents capable of suppressing the development of at least one type of immune response in vivo at doses with minimal side-effects. Some characteristics regarding the mechanism of action of corticosteroids, azathioprine, cyclophosphamide, cyclosporine and monoclonal antibodies anti-CD3 are reviewed. Corticosteroids induce a redistribution of lymphocytes and display an anti-inflammatory effect; the immunosuppressive effect of azathioprine seems to consist mainly of its suppression of the inflammatory response; cyclophosphamide and cyclosporine influence the immune system itself and anti-CD3 monoclonal antibodies suppress cellular immunity fairly specifically. Finally, a brief summary of their use in renal disease, systemic vasculitis and connective tissue diseases is given.

In a prospective clinical study we tested the immunosuppressive properties and toxicity of low-dose OKT3 induction therapy in renal transplant recipients. 50 consecutive renal transplant recipients were alternatingly assigned to low-dose OKT3 induction or prednisolone/cyclosporin. Low-dose OKT3 induction treatment consisted of 0.5 mg OKT3 twice daily for 10 days, initially combined with azathioprine and prednisolone maintenance immunosuppression that was converted to prednisolone/cyclosporin at the end of the course. During a 15-29-month follow-up period, low-dose OKT3 induction therapy was found to reduce significantly the incidence of acute rejections, as compared to the usual prednisolone/cyclosporin maintenance immunosuppression (21 versus 52%, P = 0.02). There also was a tendency towards an improved graft function after low-dose OKT3, although no significance was reached. Furthermore, compared to a historical control group of renal transplant patients in whom acute rejection was treated with 5 mg OKT3 daily, low-dose OKT3 appeared to cause fewer side-effects. We conclude that low-dose OKT3 induction therapy is superior to prednisolone/cyclosporin in preventing acute rejection after renal transplantation and that it is better tolerated than conventional OKT3 treatment.

In the present study the consequences of administration of low-dose (0.5 mg) OKT3 for respiratory side-effects and pulmonary sequestration of labelled granulocytes are compared with the known effects of 5 mg OKT3. Ten renal transplant patients were studied, of whom five were treated with 0.5 mg OKT3 and five with 5 mg OKT3. None of the patients in the 0.5 mg group and two of the patients in the 5 mg group experienced dyspnoea. Sequestration of labelled granulocytes in the lungs was significantly lower in the patients receiving 0.5 mg OKT3 compared with the patients receiving 5 mg OKT3. The simultaneously occurring peripheral blood granulocytopenia was significantly more severe in the 5 mg group than in the 0.5 mg group. We suppose that this sequestration of circulating granulocytes in the lungs is at least partly mediated by complement activation products. In vitro it is demonstrated that fixation of complement activation products on peripheral blood lymphocytes depends on the concentration of OKT3 present in the culture medium. We conclude that respiratory side-effects shortly following infusion of OKT3 are related to complement-induced pulmonary leucostasis, the degree of which is dependent on the administered dose of OKT3.

The use of OKT3 is associated with severe clinical side-effects. Adverse reactions are partly attributed to release of tumour necrosis factor (TNF). TNF binds to two receptors on the outer membranes of most human cell lines. Shedding of these proteins (sTNFR-p55 and sTNFR-p75) may block biological effects of TNF. Here we show a fair correlation between serum levels of sTNFRs and renal function as measured by glomerular filtration rate (GFR). In addition we assessed levels of sTNFR-p55 and sTNFR-p75, corrected for reduced renal clearance, in renal allograft rejection and following treatment with OKT3. Corrected serum levels (CSL) of sTNFR-p55 and sTNFR-p75 were determined in 12 renal allograft patients treated for an acute rejection episode with either OKT3 or methylprednisolone (MPNS). Serum levels of CSLsTNFR-p55 and CSLsTNFR-p75 in both groups prior to anti-rejection treatment were not elevated. CSLsTNFRs peaked at 1 h after the administration of OKT3, whereas in the MPNS group CSLsTNFRs remained unchanged. We conclude that in acute renal transplant rejection CSLsTNFRs increase after treatment with OKT3. In spite of high circulating sTNFRs levels all OKT3-treated patients suffered from clinical side-effects.

CAPD-related peritonitis was used as an in-vivo model to study Il-8 during peritoneal inflammation. Eleven episodes were studied in nine patients, who were followed on 8 consecutive days from the start of peritonitis and once after recovery (control). Il-8 was measured in dialysate (night dwells) and serum. The Il-8 time course was compared to Il-6 and TNF alpha. In addition, an in-vivo relationship between dialysate Il-8 and intraperitoneal accumulation of neutrophils was studied. A highly increased peritoneal appearance rate of Il-8 was found in the acute phase that decreased to control values during recovery. A remarkable parallelism was observed for dialysate Il-8 and Il-6 with respect to the time course and the peritoneal appearance rate. In contrast, the appearance rate of TNF alpha was much less and had a different time course. In three of four cases where the dialysate Il-8 peak occurred on day 2, the dialysate Il-6 peak still coincided with Il-8, in contrast to TNF alpha (always day 1). Dialysate Il-8 generally exceeded serum concentrations during the entire follow-up, indicating intraperitoneal Il-8 synthesis. A positive correlation was present between the dialysate Il-8 peak and the maximal number of neutrophils in dialysate. This relationship was absent for Il-6 and TNF alpha. In five of six episodes where neutrophils were quantified on both day 1 and 2, the Il-8 peak occurred simultaneously with the neutrophil peak. These findings suggest that Il-8 is involved in the recruitment of neutrophils towards the dialysate during peritonitis.

In order to study the activation of the complement system via the classical pathway we have attempted to raise antibodies specific for C4 activation products. Of 20 mouse monoclonal antibodies (mAbs) obtained, one appeared to react with an activation dependent epitope exposed on the activation products C4b, C4bi, C4c (C4b/c) as well as on iC4, but not on native C4. Using this antibody as a capture antibody and polyclonal biotinylated antibodies against C4 as detecting antibodies we developed an ELISA for the quantification of C4b/c in biological fluids. The lower limit of detection was approximately 0.025 nmol C4b/c per litre. Mean C4b/c levels in plasma samples collected from healthy volunteers in tubes containing 10 mM EDTA and 0.05% (w/v) polybrene, final concentrations, appeared to be 30 nmol/l. The potential of the ELISA procedure for evaluating complement activation in clinical samples was demonstrated.

Serum and urine interleukin-6 (IL-6) levels and serum neopterin/creatinine ratios were longitudinally studied in 86 renal transplant recipients until 4 months after transplantation. During acute rejection and acute tubular necrosis (ATN), serum and urine IL-6 levels were elevated compared to during stable transplant function (P < 0.001). During acute rejection, serum IL-6 levels increased at least 2 days before plasma creatinine started to rise (P < 0.05), indicating its early involvement in the rejection process. During cytomegalovirus (CMV) disease, serum, but not urine, IL-6 levels were higher (P < 0.01), and serum neopterin/creatinine values were higher than during stable transplant function, ATN, or acute rejection (P < 0.01). No significant differences with stable transplant function occurred during cyclosporin A toxicity. Measurement of serum IL-6 provided a sensitivity of 84% and a specificity of 85% for the diagnosis of acute rejection episodes not coinciding with ATN. All cases of CMV disease could be diagnosed by measurement of serum neopterin/creatinine, which provided a specificity of 73%.

Interleukin-6 is involved in T-cell activation and possibly plays a role in the pathogenesis of acute rejection of transplanted organs. This is indicated by elevated levels of interleukin-6 in serum and urine of renal allograft recipients, and elevated amounts of mRNA for interleukin-6 in all different cell types of the renal allograft during acute rejection episodes. However, transplant recipients receive immunosuppressive drug therapy which may inhibit production of interleukin-6 at the post-transcriptional level. Therefore, the aim of the present study was to detect interleukin-6 in biopsies taken during acute renal allograft rejection by immunohistochemical staining. In addition, serial sections were stained with cellular markers to identify interleukin-6-producing cells. In biopsies taken during acute rejection (n = 7), interleukin-6 could be detected in tubular cells (7/7) mesangial cells (3/7) and monocytes/macrophages (4/7), but not in vascular endothelium or lymphocytes. In control biopsies weak interleukin-6 staining of tubular cells only was present or there was no staining at all. We conclude that interleukin-6 is actually produced in the renal allograft during acute rejection, and that elevated urinary interleukin-6 levels during acute rejection seem to originate mainly from synthesis of interleukin-6 by renal tubular cells.

We investigated whether day to day changes in the transport characteristics of the peritoneal membrane to macromolecules in patients treated with CAPD, were related to the levels of interleukin-6 (IL-6) in the effluent of an overnight dwell. Four stable CAPD patients without peritonitis collected all "nightbags" on consecutive days during 2 months for the determination of peritoneal IgG clearance. Serum samples were obtained weekly. IL-6 was determined in the effluent on all occasions where the IgG clearance was less than mean - SD or greater than mean + SD. On these days clearances of beta 2-microglobulin, albumin and alpha 2-macroglobulin were determined as well, to calculate the peritoneal restriction coefficient, i.e. the slope of the power relationship between protein clearances and their free diffusion coefficient in water. This coefficient was used as a parameter of the intrinsic permeability of the membrane. IL-6 was measured by a sensitive and specific bioassay, using the B13.29, subclone 9.9 hybridoma cell assay. Dialysate IL-6 was measured on 43 occasions when IgG clearance was high and on 37 occasions when IgG clearance was low. In all 4 patients indirect evidence was found for local production of IL-6 within the peritoneal cavity: mean dialysate/serum ratios were 15 to 452 times higher than could be expected when IL-6 would enter the dialysate by diffusion only. The patient with the highest dialysate/serum ratio showed higher clearances of albumin, IgG and alpha 2-macroglobulin than the other 3 patients (p less than 0.001) and a lower restriction coefficient (p less than 0.001), indicating a high intrinsic permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

T gamma/delta lymphocytes are able to perform allospecific cytotoxicity and natural killer cytotoxicity in vitro. However, very little is known about their function in vivo. To investigate the possible involvement of T gamma/delta lymphocytes in the immune response to renal allografts, fine-needle aspiration biopsies and peripheral blood of 15 renal transplant recipients were studied during the first 4 weeks after transplantation. In addition peripheral blood of patients before transplantation, half a year and one year after transplantation was studied. No increase in the percentage of T gamma/delta lymphocytes in the fine-needle aspiration biopsies, including those taken during acute rejection episodes, was found. A significant decrease in the percentage of T gamma/delta lymphocytes was observed in peripheral blood after transplantation. We conclude that T gamma/delta lymphocytes seem to play no major role in the immune response to renal allografts.

Interleukin-6 (IL-6) levels were determined in the serum of 14 HIV-1-infected patients with Kaposi's sarcoma, 10 HIV-1-infected patients without symptoms, and 10 healthy male subjects. IL-6 levels were also determined in the serum of the 14 patients with Kaposi's sarcoma during treatment with high-dose human recombinant interferon-alpha (IFN alpha). Serum IL-6 levels were significantly higher in the patients with Kaposi's sarcoma than in the HIV-infected patients without symptoms and the controls. There was no consistent pattern of changes of IL-6 levels during IFN alpha treatment. These results support the view that IL-6 is a cytokine involved in the pathogenesis of AIDS-associated Kaposi's sarcoma, but appear to argue against an effect of IFN alpha on the production or release of IL-6 as an important mechanism of action of IFN alpha.

Immunosuppressive drugs are agents capable of suppressing the development of at least one type of immune response in vivo at doses with minimal side-effects. After an introduction in which different types of immune responses are briefly discussed, some characteristics regarding the mechanism of action of prednisolone, azathioprine, cyclophosphamide and anti-lymphocyte serum (ALS) will be reviewed. Corticosteroids display mainly an anti-inflammatory effect. The immunosuppressive effect of azathioprine is questionable, cyclophosphamide influences the immune system itself and ALS suppresses fairly specific cellular immunity.

We have examined the role of interleukin 2, interferon-gamma and interferon-alpha in the generation of natural cytotoxic (NC) activity and cytotoxic T-lymphocyte (CTL) activity in peripheral blood lymphocyte cultures stimulated with influenza virus, using the immunosuppressive effects of prednisolone. In addition to an inhibitory effect on the generation of CTL activity, prednisolone also inhibited the generation of NC activity in a similar dose-and time-dependent manner. Prednisolone suppressed the production of interferon-gamma when it was added on the first day of culture of PBL with influenza virus. Levels of interferon-alpha were not affected. The effects of prednisolone on the generation of NC activity and CTL activity in kinetic terms were not paralleled by the effects on interferon-alpha and interferon-gamma production. The diminished generation of NC activity could be reversed by the addition of interleukin 2 (IL-2), but interferon-gamma had little if any restorative effects. Interferon-alpha had no effect. These findings support the hypothesis that IL-2 is the major inducer of NC activity in CTL generation cultures. The inhibitory effect on CTL generation could only be reversed by IL-2 and not by interferon-alpha- and interferon-gamma. Thus, in the absence of IL-2, interferon-alpha and interferon-gamma cannot support the generation of CTL activity or the concomitantly induced NC activity.

When lymphocytes from human peripheral blood were labeled with In-111 oxinate, several of their properties appeared to be affected. The spontaneous release of the radionuclide was found to be relatively high. Labeled lymphocytes showed a decreased proliferative capacity, dependent on the dose of the label. Cytogenetic studies revealed that In-111 oxinate induces severe chromosomal aberrations. These results emphasize the need for great caution in the use of the In-111 label for studies on lymphocyte traffic in humans.

Oral administration of prednisolone (in single doses of 10, 30, or 60 mg) to healthy volunteers was found to affect the T lymphocytes in the blood with regard to binding of monoclonal antibodies and lactate dehydrogenase isoenzyme pattern. The findings indicate that these effects are dependent on the dose of the drug and the time after the administration of the drug. Prednisolone induces a T lymphocytopenia in the peripheral blood that affects OKT4-positive lymphocytes more than OKT8-positive lymphocytes, resulting in a slight decrease in the ratio OKT4/OKT8. Moreover, the lactate dehydrogenase isoenzyme pattern changes, resulting in a decrease of the H/M ratio of this enzyme. The proliferative responses of peripheral blood lymphocytes are not affected after a single dose of 10 mg. However, after administration of either 30 or 60 mg of prednisolone, the proliferative responses are decreased to a different extent, depending on the stimulus used. In vitro experiments are presented showing that any effect of prednisolone on nonstimulated lymphocytes is reversible. Based on the observed changes in OKT pattern and lactate dehydrogenase isoenzyme profile of the T lymphocytes induced by administration of prednisolone, it is concluded that the drug induces a temporary depletion from the peripheral blood, preferentially of high-reactive T lymphocytes. As a consequence, the peripheral blood compartment is enriched for T lymphocytes with a low H/M ratio of lactate dehydrogenase isoenzymes, known to be less reactive to proliferative stimuli.

Natural killer-cell activity for K562 target cells was measured in 13 patients with severe combined immunodeficiency before bone marrow transplantation. Both unseparated peripheral blood mononuclear cells and sorted cell subsets (B73.1 positive, B73.1 negative, OKT3 positive, OKT3 negative) were tested. Heterogeneity of natural killer-cell activity was observed, the level of which did not correlate with the usual subdivision of severe combined immunodeficiency, as defined by a scientific group on immunodeficiency for the WHO. In those patients in whom natural killer-cell activity was observed in unseparated cells, testing of this function in sorted cell subsets revealed some unexpected findings. In three of four patients, B73.1-negative cells showed remarkable natural killer-cell activity. In addition, in one of these patients, no activity was observed in the B73.1-positive cells.

In a group of eight patients suffering from clinically definite multiple sclerosis, we studied the effects of treatment with cyclophosphamide on the immune reactivity in vitro and in vivo. The results are compared with those obtained in a control group consisting of eight patients who received no drug therapy and who were matched with the former group for age, sex and severity of disease. The results indicate that therapy with cyclophosphamide at a mean dose of 100 mg/day induces a profound lymphocytopenia in peripheral blood involving both T and B cells. Serum levels of immunoglobulins as well as primary and secondary antibody responses were depressed. In tests with standardized cell numbers, proliferative responses of lymphocytes in vitro and cytotoxic T cell function remained normal, whereas K and NK cell activities were diminished. Secondary cellular immune responses in vivo remained intact; however, the primary cellular immune response in vivo was markedly depressed. From these data, it is concluded that therapy with cyclophosphamide in man mainly affects humoral immune functions, but also cellular immunity, although to a lesser extent.

The effects of chemotherapy with either Chap-5 (a drug regimen consisting of adriamycin, cis-dichlorodiammine platinum (II), hexamethylmelamine and cyclophosphamide) or Hexa CAF (a drug regimen consisting of methotrexate, 5-fluorouracil, hexamethylmelamine and cyclophosphamide) on the immunocompetence of 22 patients with advanced ovarian carcinoma were studied. Both primary and secondary humoral and cellular immune responses in vivo were studied. In addition, the numbers of granulocytes, lymphocytes and monocytes in peripheral blood were determined, as well as the levels of immunoglobulins and complement proteins. Furthermore, the proliferative capacity of lymphocytes, cytotoxic T-cell function, and K- and NK-cell activities were measured. The results indicate a depression of the primary humoral immune response in vivo in patients receiving Chap-5. Furthermore, a decrease of several parameters in vitro was observed. However, these alterations were only moderate and rapidly reversible.

A relatively simple assay with improved reliability and sensitivity for measuring levels of 6-mercaptopurine in human plasma is presented. After extraction of the compound and the added internal standard with phenyl mercury acetate, samples were separated by ion-pair reversed-phase high-performance liquid chromatography. On-line the analytes were oxidized to fluorescent products and detected in a flow-fluorimeter. The within-day coefficient of variation was 3.8% at a concentration of 25 ng/ml. The lower detection limit was 2 ng/ml when 1.0 ml of plasma was used. Mercaptopurine concentration versus time curves of two subjects after a single oral dose of azathioprine are shown.

A 63 year old man with late onset hypogammaglobulinaemia is described. Splenectomy, carried out because of marked splenomegaly and pancytopenia, demonstrated marked T lymphocytic infiltration in the splenic red pulp with prominent germinal centres. A persistent peripheral blood and bone marrow lymphocytosis ensued (10 X 10(9)/l and 40% respectively) and this was consistent with T-chronic lymphocytic leukaemia (T-CLL). Over 88% of his blood lymphocytes were E+, OKT3+, OKT8+ and OKT11+; 54% of the T lymphocytes had receptors for IgG (T gamma cells). Functional studies showed that the T lymphocytes of this patient lacked killer and natural killer cell function but they effectively suppressed the differentiation of normal B cells in a PWM stimulated system. It is suggested that the T-CLL in this patient resulted from the proliferation of the T suppressor subset which was responsible for his hypogammaglobulinaemia.