HLA in kinship determinations among Haitian immigrants

Immunogenetic study of alleged first-degree relatives was undertaken among 258 prospective United States immigrants from Haiti. Methods involved serotyping red cells for ABO, Rh, and MN antigens and typing leukocytes for HLA, A, B, and C locus antigens. Kinship was definitely excluded in a relatively low 4.2% of cases involving putative parents and children. Among cases involving alleged siblings, estimates of fraud appeared slightly higher, but the method is suspect because even in true sibships, there may be an absence of obligatory gene markers. Data suggests that some cases involved half-siblings rather than fraud. Of demonstrated exclusions of parent or child, HLA detected the lack of kinship in 87.4% versus 16.9% by red cell typing. However, there were cases in which exclusions were found by red cell methods alone; furthermore, red cell plus HLA typing allows for a calculation of probability of kinship that is analogous to calculations in paternity studies. Together, the red cell and leukocyte systems offer a prior probability of exclusion of parent-child relationships in 91.3%.

The reversible binding of vinblastine to platelets: implications for therapy

The ability of platelets to adsorb vinblastine has been used to treat patients with immune thrombocytopenia. It is hypothesized that the drug-platelet complex is coated with antibody, taken up by macrophages which are then destroyed by the drug. We gave 16 courses of vinblastine-platelets to six patients with immune thrombocytopenia. Only one patient responded, and therefore we examined possible reasons for the lack of benefit. Using 3H-vinblastine, the kinetics of vinblastine binding to platelets was studied in vitro. The binding of vinblastine to both human and rabbit platelets was identical with maximal binding occurring within 10 min at 600 microgram/ml vinblastine. Similarly, the plasma half-life of vinblastine in rabbits was close to that reported for man, and therefore, in vivo binding of vinblastine to platelets in rabbits was considered a suitable model for man. Homologous donor rabbit platelets were labeled with 51Cr alone, 51Cr plus vinblastine, or 3H-vinblastine and infused into recipient rabbits. Vinblastine had no effect on 51Cr survival, but all measureable vinblastine had left the platelets within 2 hr of the infusion. These observations suggest that delivery of the vinblastine to the macrophages depends on the platelets being phagtocytized before the drug leaves the platelets. This would be likely to occur only in those patients with severe immune thrombocytopenia. Further investigations into this treatment should be directed at methods to maintain the drug within the platelet.

Thrombotic Thrombocytopenic Purpura: Mechanism for Effectiveness of Plasmapheresis

Thrombotic thrombocytopenic purpura (TTP) is a rare but serious illness of unknown etiology. Treatment by plasmapheresis has been reported to be effective but the mechanism for benefit is unknown. We have investigated the effect of plasmapheresis in 2 patients with TTP by quantitating platelet associated IgG (PAIgG) levels prior to and following plasmapheresis. Both patients had very high levels of PAIgG at presentation (90 and A8 fg IgG/platelet respectively, normal 0-5). in both, the PAIgG levels progressively fell to within the normal range and the platelet count rose following plasmapheresis. One patient remained in remission with normal platelet counts and PAIgG levels. The other relapsed after plasmapheresis and the PAIgG level rose prior to the fall in platelet count. Plasmapheresis was repeated and resulted in normalization of both the platelet count and PAIgG level. It is suggested that plasmapheresis removes antiplatelet antibody or immune complexes which may be of etiological importance in this illness.

Thrombotic Thrombocytopenic Purpura: Mechanism for Effectiveness of Plasmapheresis

Thrombotic thrombocytopenic purpura (TTP) is a rare but serious illness of unknown etiology. Treatment by plasmapheresis has been reported to be effective but the mechanism for benefit is unknown. We have investigated the effect of plasmapheresis in 2 patients with TTP by guantitating platelet associated IgG (PAIgG) levels prior to and following plasmapheresis. Both patients had very high levels of PAIgG at presentation (90 and 48 fg IgG/platelet respectively, normal 0-5). In both, the PAIgG levels progressively fellto within the normal range and the platelet count rose following plasmapheresis. One patient remained in remission with normal platelet counts and PAIgG levels. The other relapsed after plasmapheresis and the PAIgG levelrose prior to the fall in platelet count. Plasmapheresis was repeated and resulted in normalization of both the platelet count and PAIgG level. It is suggested that plasmapheres is removes antiplatelet antibody or immune complexes which may be of etiologicalimportance in this illness.