A cytotoxic human‐human hybridoma antibody (TrH6) specific for HLA‐DRw52

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Abstract
TrH6 is a new human‐human hybridoma antibody (Ab) of IgM, lambda isotype. At concentrations of 17–5000 ng IgM/ml, TrHó killed twelve out of fourteen lymphoblastoid cell lines that expressed DRw52, but none of the nine DRw53 homozygous lines. Both DRw52+ cells (LUY, TAB) not killed by TrH6 were DR8+, suggesting that these lines express a structural variant of DRw52 linked to DR8. The murine cytotoxic DRw52‐specific mAb 7.3.19.1 (Koning et al. 1984) exhibited the same pattern of reactivity with DRw52+ cells as TrH6. However, unlike TrH6, 7.3.19.1 cross‐reacted weakly with two DR7+DRw53+ homozygous cell lines, suggesting that the TrH6 epitope has a more limited distribution. The reactions with a panel of cells with known deletions in the HLA‐region supported the conclusion that TrH6 is specific for DRw52. Further evidence was obtained in a competition RIA, where the murine mAbs L243 (anti‐DR monomorphic) and 7.3.19.1 (anti‐DRw52) inhibited binding of radiolabeled TrH6 to DRw52 homozygous cells. TrH6‐coated magnetic beads provided a simple rosette‐assay for typing of “buffy‐coat” leukocytes for the TrH6 epitope.