Occurrence of lymphocytotoxins in multi‐case rheumatoid arthritis families: relation to HLA

The presence of lymphocytotoxic antibodies (LCA) and their association with HLA haplotypes has been studied in 27 multi‐case rheumatoid arthritis (RA) families (13 multiplex and 14 simplex) in Northern India. Of the total 59 RA patients, 69.4% had cytotoxins in their sera as compared with 2.5% of healthy controls. No differences were observed in the frequency of LCA in relation to sex and rheumatoid factor. LCA against B cells were significantly more predominant than those against T cells. Twenty families studied for correlation of HLA with LCA showed greater intensity of reaction with DR4⁺ haplotypes, particularly in simplex families. Similarly, the frequency of LCA among patients and unaffected parents was greater in simplex compared with multiplex families. Haplotype sharing with the patient was increased in the relatives positive for cytotoxins in these families. An immunogenetic contribution made by the affected parent and B common environmental stimulus may be responsible for the increased production of LCA in multi‐case families with RA.