[Study of the HLA-DQ system by the complement fixation test on lymphocytes stimulated by phytohemagglutinin. Existence of HLA-DQX allele(s)].

The complement fixation microtechnique against PHA blasts has been used to study HLA-DQw1, 2, 3 specificities with sera from multiple transfused patients and/or from multiparous women. Several sera (6 or 7) have been used to define each DQ specificity. The sera have been chosen because of their reactivity with cells from HLA-DR 1, 2 or w6 donors (for DQw1), DR3 or 7 donors (for DQw2,) DR4 or 5 donors (for DQw3). Correlation coefficients between DQ and DR specificities were from 0.56 to 0.91. Correlation coefficients between sera were from 0.51 to 0.92 in each cluster of sera. The segregation of DQw1, 2, 3 specificities has been studied in 46 families with 234 children. This study showed haplotypes lacking DQw1, 2, 3 specificities. The segregation of such 11 DQX haplotypes has been observed in 38 children from 8 families; 5 children were DQX/DQX homozygotes. Up to now, no serological reagent defining the specificity (or specificities) corresponding to DQX has been found. No preferential association was observed between DQX and DR specificities. The gene frequencies observed in 170 haplotypes in these 46 families were as follows: DQw1: 0.400; DQw2: 0.252; DQw3: 0.282; DQX: 0.065. Detecting DQ specificities seems easier by CF on PHA blasts than by lymphocytotoxicity microtechnique against B lymphocytes and monocytes from pheripheral blood. This suggests that PHA blasts express larger quantities of DQ molecules than B lymphocytes and monocytes. The results confirm that complement fixation microtechnique against PHA blasts is efficient for HLA-DQw typing.