Homogeneity of the HLA-linked SB2 and SB3 specificities demonstrated by cloned alloreactive T cells.

The HLA-linked "SB" antigens comprise a new segregant series of B-cell alloantigens mapping between HLA-DR and glyoxylase. They can be detected by secondary proliferative responses of lymphocytes primed against HLA-A, B, C, DR, MB- and MT-compatible stimulators. To asses genetic complexity of the SB-gene region, alloreactive cloned T-cell lines were derived from four reagents detecting specificities designated SB2 and SB3. In two families, products detected by seven different clones segregated with the HLA haplotypes bearing the SB2 or SB3 specificities as recognized by the uncloned reagents. There were no indications that the cloned cells differed from the oligoclonal reagents in their fine specificity. In contrast to previous results with an SB4-associated specificity, in population studies of 25 SB2-positive and 23 SB3-positive donors, no evidence could be found for subtypes of either specificity. Thus, even at the level of recognition by cloned T-cells, both SB2 and SB3 appear to be remarkably homogeneous in the population.