Mariaclara Belvedere

Split of HLA-DRw2 into subtypic specificities closely correlated to two HLA-D products

Two B-lymphocyte-specific human alloantisera were studied, PA59 and 51.23. They identify two new HLA-DR alleles, which are both subtypic to HLA-DRw2. Moreover, they are closely correlated with two HLA-D products, Dw2 and tb24 (tb24 is a new specificity described by our group). Thus, DRw2 can be “split” into two subtypic specificities that have been named TO60 and TO61, which appear more strongly correlated with HLA-D antigens. Absorption studies demonstrated cytotoxicity-negative, absorption-positive (CYNAP) reactions, and cross-reactive groups of antibodies.

An antibody cross-reacting with LA and FOUR antigens of theHL-A system

A volunteer was immunized by planned blood transfusions from an LA and FOUR incompatible donor. Among the several antibodies produced, an antibody population was found that cross-reacts with both LA and FOUR antigens; both these crossreacting determinants were present in the immunizing donor. Monospecificity of the antibody has been proven by adsorptions and elutions. Resistance to lysis experiments excluded the possibility that this antibody does not react against LA and FOUR, but reacts instead against an antigen belonging to another independentHL-A locus with alleles in strong linkage disequilibrium withLA andFOUR alleles. The following hypotheses are therefore formulated: a)LA andFOUR factors have structural analogies; b) LA and FOUR molecules lie in close proximity on the cell surface so that the appearance of a “hybrid” antigenic determinant becomes possible.

An enzymatic method for microdetermination of aphidicolin: A promising anticancer drug

We have developed a method, based on the in vitro inhibition of purified human DNA polymerase alpha, the major enzyme of DNA replication, which allows the rapid and accurate determination of pmol amounts of aphidicolin, a promising anticancer drug. The efficacy of this simple method was verified by the determination of aphidicolin in the liver, spleen, blood and urine of mice treated parenterically with the drug. Given its sensitivity and the avoidance of radioactive tracers, this enzymatic method is suitable for the determination of the drug in body fluids and tissue biopsies from living humans. It allows the detection and quantitation of aphidicolin in the presence of inactive metabolite(s) with very similar chemical structure(s) such as those generated by liver microsomal oxidases. The technique will also be useful to monitor the purification of the drug from cultures of Cephalosporium aphidicola.

Sera from Volunteers Immunized by Planned Blood Transfusions as a Source of Dr Cytotoxic Typing Reagents

Sera from volunteers immunized with planned blood transfusions were tested for anti DR cytotoxic antibodies with a panel of HLA typed cultured human lymphoid cells using a variety of serological techniques. The majority of sera contained DR cytotoxic antibodies. The specificity of DR antibodies in seven sera was determined by testing them with a panel of B peripheral lymphocytes typed with DR alloantisera submitted to the 7th International Histocompatibility Workshop. The temporal evolution of DR and HLA-A and B cytotoxic antibodies was determined in two subjects by testing serial bleedings with B lymphoid cells, coated with Fab2 fragments from anti beta 2 mu and anti DR xenoantisera. Results indicated a parallel evolution of DR and HLA-A and B cytotoxic antibodies.

XENOANTISERA TO DRw ALLOSPECIFICITIES

The specificity of DR xenoantisera was assessed by testing them with a panel of HLA typed B‐lymphocytes in a cytotoxic test with rabbit or human complement. The pattern of reactions of some xenoantisera correlated with DR allospecificities. These results confirm that injection of DR antigens across species barrier can elicit antibodies to DR allospecificities.

Fab2 FRAGMENTS FROM HLA XENOANTISERA SPECIFICALLY BLOCK CYTOLYSIS MEDIATED BY HLA-A, B ALLOANTISERA

Fab2 fragments from antisera raised in rabbits with partially purified cellular and serum HLA antigens were tested for their ability to block the cytolytic activity of operationally specific HLA‐A, B alloantisera. One Fab2 fragment preparation blocked the cytolytic activity of all the HLA‐A,B alloantisera tested; the remaining nine inhibited the lytic activity of alloantisera to certain HLA‐A,B allospecificities, suggesting that these xenoantisera contain antibody to certain HLA‐A,B allotype determinants or to closely associated structures. In contrast to previous reports in the literature none of the xenoantisera contained significant amounts of antibodies to human β2‐microglobulin.

Antigen Society #31 Report Part 2: Antigen Society #31 Report

The discovery that alloactivated T lymphocytes express new class II antigens (1,2) stimulated experiments in which activated lymphocytes were studied for the expression of new antigens not detected at the quiescen stage. Other workers have shown that resting T lymphocytes could be subdivided by the use of sera recovered from patients with juvenile rheumatoid arthritis (3) or from alloimmunized volunteers (4,5). Later (6), TCA TCB system expressed on T gamma-enriched cells was also identified by alloantisera. When PHA-activated lymphocytes were used in the screening of pregnancy sera, it appeared that some sera reacted exclusively with the lectin-activated lymphocytes, but not with the resting T or B lymphocytes separated from the same individual (7). Cross-absorption experiments indicated that, indeed, these determinants were not shared by the resting autologous lymphocytes. In blocking experiments, it was shown that the new determinants are associated with B-2 microglobulin, which classified them into the class-I gene product family.

A NEW HLA ANTIGEN APPARENTLY NOT CONTROLLED BY THE KNOWN HLA LOCI

The human allogeneic serum RM3 recognizes a lymphocyte structure inherited with the HLA chromosome. Population studies show several positive associations with antigens of the HLA‐A and HLA‐B series. Negative associations have been found with antigens of the HLA‐C series. Moreover the distribution of the RM3 factor is in Hardy‐Weinberg equilibrium with that of the HLA‐C alleles.