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

Some technical aspects of MLC inhibition by sera obtained from multiparous women were studied. The variability of the MLC response was very high. The serum source used in the cultures was probably to a large extent responsible for this variability. Aspecific inhibition, which was observed with some test sera, could be removed by dialysis against PBS. To make the evaluation of inhibition by immune sera objective, a scoring system was introduced for the degree of inhibition. Test sera were usually added to the cultures. Alternatively, stimulator and responder cells were preincubated with the test serum. Preincubation of the stimulator cells did not show a difference in inhibition pattern when this was compared with serum addition. Preincubation of the responder cells showed a completely different inhibition pattern. The MLC inhibition test compared very well with an indirect immunofluorescence test and a cytotoxicity test using B-cell enriched cell suspensions.