Clonal T-cell colony formation in agar culture: an attractive assay to test the T-cell depletion from bone marrow.

Current studies suggest that the depletion of T-lymphocytes from donor marrow is an effective method for preventing acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation in man. To deplete the T-lymphocytes from bone marrow cells we use either monoclonal anti-T-cell antibodies and complement or T101 ricin A-chain immunotoxin. Residual T-lymphocytes are analyzed by their capacity to form clonal T-cell colonies in the presence of phytohemagglutinin (PHA), accessory cells, and recombinant interleukin 2. The method is compared to immediate indirect immunofluorescence (iF) and thymidine incorporation by marrow cells stimulated by PHA. IF is not suitable for evaluating the depletion by immunotoxin, and the interpretation of thymidine incorporation is generally questionable. The results of the colony formation show that the sensitivity of the colony assay is close to that of iF when T cells are depleted by complement lysis, and the sensitivity of the colony assay is not dependent upon the depletion procedure. Therefore, the T-cell colony assay is a simple functional control for the quality of bone marrow T-cell depletion, especially for T-cell depletion by immunotoxin.

Anti-B cell lymphocytotoxic antibodies in kidney transplant recipients.

Serial serum samples from 47 renal allotransplant recipients were screened for antiperipheral blood lymphocyte, anti-B cell, and anti-Daudi cell line antibodies. Various associations of these antibodies were observed in 28 patients. Anti-Daudi did not correlate with graft survival, whereas anti-B, although they were often associated with anti-peripheral blood lymphocyte antibodies, showed the strongest correlation with chronic rejection (P = 0.00002). However anti-B cytotoxicity preceded or was concurrent with the onset of chronic rejection in only 53% of the cases. Antibodies were absent in six of nine patients with irreversible acute rejection, but they usually appeared after transplant nephrectomy. These findings suggest that anti-B cell antibodies may play a role in the rejection process. In 15 of 17 recipients (88%), anti-B cell antibodies occurred during the first trimester after transplantation. These patients showed 20% 1-year graft survival compared with 68% in those without antibodies at that time (P less than 0.005).

Genetic susceptibility to toxic epidermal necrolysis.

The pathophysiologic events leading to toxic epidermal necrolysis (TEN) remain unknown. With the idea of an immunologically mediated reaction occurring in predisposed subjects we performed HLA-A, -B and -DR typing in 44 patients surviving TEN. We observed a significant increase of only HLA-B12, previously found associated with ocular complications of Stevens-Johnson syndrome. When patients were stratified according to the drugs involved as causes for their TEN, we found other HLA phenotypes associated with B12, varying with each category of drugs. Sulfonamide-related cases of TEN were linked to A29, B12, and DR7, while oxicam-related cases of TEN were linked to A2 and B12. These results suggest that a genetic background, related to the major histocompatibility complex, may contribute to severe blistering drug reactions.

[Idiopathic nephrotic syndrome and the HLA allele. Prevalence of age-related DR7]. / Syndrome néphrotique idiopathique et allèle HLA. Prévalence de DR7 liée à l'âge.

High prevalence of HLA DR7 was well documented in idiopathic nephrotic syndrome (INS) of childhood. Our data in 43 INS, child and adult patients, did not show any significant difference from control group, specially for HLA DR7. Moreover a significant difference occurred when the data was compared in child and adult INS patients. HLA DR7 was more frequent when the nephrotic syndrome appeared before 15 years old. There was no correlation between the presence of HLA DR7 and those of allergy history or increased serum IgE level, on the opposite with previous data. The presence of DR7 would favor its onset at an earlier age. Alternatively, the difference in DR7 prevalence could be an additional argument for considering that the corticosensitivity and negative histological criteria might collect, under the same name, different glomerulopathies.

[Autoimmune thrombopenic purpura and pregnancy. Absence of thrombopenia in the newborn infant despite the presence of circulating IgG auto-antibody in the mother]. / Purpura thrombopénique auto-immun et grossesse. Absence de thrombopénie chez le nouveau-né malgré la présence chez la mère d'un auto-anticorps circulant de nature IgG.

Many pregnant women with AITP bear children with transient thrombocytopenia which is a potentially life threatening complication. Previous reports have demonstrated that monitoring of IgG circulating platelet antibodies may help with the management of these women. We report the case of a pregnant woman with AITP whose sera contained an IgG auto antiplatelet demonstrated by the fluorescein labelled antiglobulin techniques. Steroids had a beneficial effect with a return to a normal of the mother's platelet count but with no disappearance of the circulating antibody. Surprisingly the neonatal platelet count was normal and studies in the baby showed that the antibody had not crossed the placenta in detectable amounts. This case demonstrates our current inability to predict fetal thrombocytopenia and plan the mode of delivery.

HLA phenotypes and bullous cutaneous reactions to drugs.

Drug induced toxic epidermal necrolysis and Stevens-Johnson syndrome are weakly associated with HLA-B12. Among patients reacting to a given drug we observed stronger links, especially for HLA-A29; B12; DR7 and sulphonamides.

Acquired autoimmune thrombocytopenia after allogeneic bone marrow transplantation.

A 29-year-old man in remission from acute myeloblastic leukaemia was treated by chemoradiotherapy and transplantation of bone marrow (BMT) collected from his HLA identical brother. Engraftment was documented on D12. Transient acute GVHD (grade II) appeared from D34. No infection complicated the BMT. Nevertheless severe thrombocytopenia persisted and was unresponsive to marrow donor platelet transfusion. The platelet immunofluorescence test demonstrated the autoimmune basis of the thrombocytopenia. This study suggests that the transient immune imbalance observed in the early post graft period could facilitate the appearance of autoimmune cytopenias.

HLA-DR restriction in suppression of hematopoiesis by T cells from allogeneic bone marrow transplants.

Three allogeneic bone marrow transplantation patients who exhibited a suppressive subset of T cells for in vitro hematopoiesis have been investigated to determine whether this T cell suppressive effect was genetically restricted. In the three cases, T cells separated by sheep red cell rosetting inhibited blood colony-forming units granulocyte-monocyte (CFU-GM) and burst-forming unit erythroid (BFU-E) growth from the patients and from the bone marrow donors who were HLA identical, but not from randomly chosen unrelated subjects. In one case, cocultures were performed between the patient T cells and the T-depleted cells from eight siblings and from the mother. A marked inhibition (30 to 60%) of CFU-GM and BFU-E growth was found in the relatives who shared a haplo-identical HLA-DR 5. The same degree of suppression was found with respect to whether the siblings were homozygous or heterozygous for the HLA-DR 5 antigen, and whether or not they shared common class I antigens. This inhibition was totally abolished when a monoclonal antibody against HLA-DR was added, whereas a monoclonal antibody against class I histocompatibility antigen had no effect. To additionally demonstrate that this inhibition was mediated by a single HLA-DR haplotype, T cells from the patient were co-cultured with cells from three normal unrelated individuals, one with a phenotypically identical DR and two with only one haploidentical DR. Inhibition was similarly found in the subject exhibiting complete DR identity, and the subject with only the DR 5 haploidentical phenotype. These results demonstrate that a unique subset of T cells present in allogeneic bone marrow transplants specifically suppress differentiation of hemopoietic progenitors that bear one phenotypically haplo-identical HLA-DR antigen.