Homozygous DW typing cells were tested for six B‐lymphocyte specificities. All four of the second locus specificities of B lymphocytes were strongly associated with the DW specificities. DW1 typing cells were B group 6, DW2 were B4, DW3 were B5, and LD107 were B3. The first B‐cell locus antigens 1 and 2 tended to be uniform within the DW groups. From an analysis of the typing responses of a panel of cells to the homozygous typing cells, it has become apparent that the first B‐locus specificity present on the homozygous typing cells also plays a role in determining whether a typing response is obtained or not. Thus, the DW3 typing cells were themselves B2 and B5, and cells having B2‐B5 were most frequently nonreactive to DW3 in mixed lymphocyte culture. Homozygous typing cells therefore mainly detect the second B‐cell locus antigens and, to a lesser degree, the first locus specificities. Stated another way, homozygous typing cells do not define a single specificity, but rather the presence of two B‐lymphocyte specificities, even though their responses often reflect matching of only the second B‐locus specificity.

Thirty families in whom at least one member had asthma were typed for five new B-lymphocyte specificities, as well as the antigens of the A and B loci of HLA. The B-cell reactions were consistent with the concept that they were determined by genes linked to the HLA-A and HLA-B loci. Between 22 HLA-identical siblings and 16 two-haplotype different siblings, a significant difference in concordance of reactions for the B-cell groups was noted. The data obtained were most compatible with B-groups 1 and 2 being determined by one locus and B-groups 3, 4, and 5 by another locus. The superhaplotypes of HLA-A, HL-B, and B-cell loci 1 and 2 were then determined. The most striking linkages noted were for the second B-cell locus and the HLA-B locus: B-cell group 3 with HLA-B12, B-cell group 4 with HLA-B7, and B-cell group 5 with HLA-B8, B17, and Bw35.

A total of 950 MLC combinations were set up out of which 259 were classified as low MLC response. An attempt was made to predict which of the combinations would give low response by matching the B-lymphocyte specificities and the HLA-A and -B antigens. A statistically significant prediction of a low response was noted for the B-lymphocyte specificities as well as for HLA-A and -B antigens. The fraction of the low response, which was correctly found, was, however, greater with the B-cell specificities than the HLA-A and -B locus antigens. It is concluded that the B-lymphocyte specificities may be either identical or closely linked to the DW specificities. To what extent they are associated with the strong transplantation antigens of man remains to be determined.

30 families in which at least one member had asthma were tested for five new specificities of B lymphocytes as well as for twenty-five HLA antigens. 41 other asthmatic patients were also tested. HLA-B8 was slightly less common than normal in the 71 patients with asthma and there was a trend towards an increased frequency of HLA-A2 in these patients. However, 88% of the 30 asthma patients had B lymphocyte group 2 compared with 24% of the 109 controls. This strong association between asthma and B lymphocyte group 2 was not completely paralleled by linkage with a postulated susceptibility gene of the HLA complex in 9 families whose members were investigated in detail.