Secondary response of in vitro-primed human lymphocytes to allogeneic cells

In vitro-primed human lymphocytes proliferate in a secondary mixed lymphocyte reaction (MLR) under the control of MLR-S specificities. HL-A antigens are unable to induce a secondary Proliferation. In familial haploidentical combinations, the secondary proliferation is specific for the priming MLR-S specificity, i.e., as early as 24 to 48 hours after the re-stimulation, a clearcut response is observed toward the sensitizing MLR-S specificity. The secondary response is reflected in acceleration of the reaction rather than in the peak of (³H) TdR uptake. However, when either haploidentical familial primed responding cells or unrelated cells primed toward MLR-S homozygous cells were used, no early typing response was observed against unrelated cells. The level of (³H) TdR incorporation toward cells which possessed and those which did not possess the priming specificity was identical until day 3–4. Noneless, the peak response toward cells possessing the priming MLR-S specificity occurs regularly 24 to 48 hours prior to the peak response toward the cells negative for the priming specificity (day 3–4 as opposed to day 5). Technical improvements are therefore needed before such a technique will provide a clearcut MLR-S typing methodology.