MODULATION OF THE T-CELL COMPARTMENT BY BLOOD-TRANSFUSION - EFFECT ONCYTOTOXIC AND HELPER T-LYMPHOCYTE PRECURSOR FREQUENCIES AND T-CELL RECEPTOR V-BETA USAGE

Recent data suggest that the favorable effect of pretransplant blood t ransfusion (BT) on transplant outcome depends on the HLA match. HLA-DR or haplotype shared transfusions lead to transplantation tolerance, a nd HLA-mismatched BT leads to immunization. The immunological mechanis m involved is still unknown. To investigate the effect of HLA compatib ility between blood donor and recipient on the T cell compartment, we determined the frequency of cytotoxic and helper T cell precursors spe cific for blood donor cells (n=20) and the T cell receptor V beta (TCR BV) repertoire of the CD4- and CDS-positive peripheral blood mononucle ar cells before, at 2 weeks after, and at more than 10 weeks after ET (n=10). Patients had received one transfusion of a nonstored (<24 hr a fter withdrawal) erythrocyte concentrate without buffy coat containing on average 6x10(8) leukocytes. Eight patients shared an HLA-B and -DR antigen, nine patients shared one HLA-DR, antigen, and three patients shared no HLA class LI antigens with the blood donor. All patients sh owed a significant increase in both cytotoxic and helper T cell precur sor frequencies against the blood donor 2 weeks after BT. In most pati ents, the frequencies reached pretransfusion levels again long after B T. In 5 of 10 patients, an expansion of one or more TCRBV families was observed in either the CD4 or CD8 compartment. This study demonstrate s that BT, irrespective of the degree of HLA matching, induces activat ion of the T cell compartment. The degree of sharing of HLA antigens w as not correlated with quantitative changes in cytotoxic T lymphocyte precursor or helper T lymphocyte precursor frequencies, or changes ind uced in the TCRBV repertoire. Cytotoxic and helper T lymphocyte precur sor frequencies and TCRBV repertoire determined after BT do not give a n indication for a state of tolerance prior to transplantation.