Inhibition of the mixed leukocyte reaction by alloantisera in man. I. Technical aspects

Multiparity induces priming to male-specific minor histocompatibility antigen, HY, in mice and humans

One of the factors that increases the risk of graft-versus-host disease following allogeneic stem cell transplantation is the use of multiparous females as donors. Since minor histocompatibility (H) antigens are the main targets of graft-versus-host and graft-versus-leukemia responses, we tested the hypothesis that multiparity could prime minor H antigen-specific T cells. We examined the peripheral lymphoid populations of multiparous mice and humans for evidence of priming of CD8+ T-cytotoxic lymphocytes against peptide epitopes of the male-specific minor H antigen, HY. In contrast to naive females, multiparous females have measurable levels of circulating HY-specific tetramer-positive T lymphocytes, which can be readily expanded in vitro. These findings have implications for the in vitro generation of T-cell clones as reagents for immunotherapy for tumors following stem cell transplantation.

Possible mechanisms by which alloantisera inhibit in the MLC test

MLC inhibition studies were performed with two human alloantisera: one specific for HLA-B7, the other for HLA-DRw7. The stimulator cell inhibitory effects of these sera were tested in primary and secondary MLC tests. Both sera inhibited in the primary MLC, whereas only the anti-DRw7 serum was capable of blocking the secondary MLC test. The difference in inhibiting properties of these sera was further analyzed in primary MLC tests using selected MLC combinations, Fc receptor negative cell populations and pepsin digests of the anti-B7 serum. Anti-DRw7 antibodies could inhibit by masking the stimulatory DR antigens. The inhibition of the anit-B7 antiserum was dependent on Fc, which suggested that anti HLA-B antibodies inhibited by some other mechanism. This inhibition could have been caused by antibody dependent cellular lympholysis of the stimulator cells or by the induction of suppressor cell activity.

Inhibition of MLC stimulator function by antibodies directed to non-HLA antigens

The properties of five human alloantisera which inhibit the stimulating capacity of cells in an MLC reactions are described. All of the sera showed patterns of inhibition in families which did not correlate with HLA haplotypes. In a large proportion of the families investigated the sera did not react with parental cells but inhibited the cells from one or more of the children. Absorptions were performed with one of these sera using such non-reactive parental cells. Paternal cells absorbed out the inhibiting activity while maternal cells did not. This indicates that expression of the antigen with which the inhibiting antiserum reacts is insufficient for inhibition and other factors, either environmental or inherited from the mother, influence the capacity of the antiserum to cause inhibition. This antigen was most likely a non-HLA antigen.

Can anti HLA-A and -B antibodies inhibit the MLC test?

Eleven lymphocytotoxic pregnancy sera were tested for inhibition in the MLC test. Responder inhibition and stimulator inhibition were analyzed separately by using cells from the serum producer as stimulator and responder respectively. Only three sera showed inhibitionof responder function, whereas all sera showed inhibition of stimulator function. The specificity of the latter inhibition was at least in part attributable to antibodies directed to specificities other than B-cell specificities (presumed to be coded for in the HLA-D region). This was deduced from the fact that platelet eluates devoid of anti B-cell antibodies effectively inhibited in MLC.