Evidence against HLA and immunological dependence of disease outbreak in SLE. Immunological characterisation of identical twins clinically discordant for SLE.

Identical female twins clinically discordant for 20 years for SLE were studied. Their HLA-haplotype was A1,28; B8w6,w35; Cw3,w7; Dr3,4. Both twins had a raised erythrocyte sedimentation rate, autoantibodies, and circulating immune complexes. The diseases sibling had a reversed OKT4/OKT8 ratio (0.43), decreased helper T cell number, defective pokeweed mitogen (PWM) induced plasma cell differentiation, and overactive hydrocortisone sensitive suppressor cells. Immunological abnormalities may be only partly HLA related (B8; Dr3), but are most probably secondary to the disease process in the sibling with SLE. Exogenous and/or endogenous factor(s) other than genetic or immunological are suggested as being operative in the predisposition to and expression of SLE.