No abstract

The families of 29 patients with systemic lupus erythematosus and 42 normal subjects were studied to determine the inheritance of the HLA-A, B, C, and DR antigens and also the complement polymorphisms for C2, C4A, C4B, and Bf, which are encoded in the same region of the sixth chromosome. Null (silent) alleles for C4A, C4B, or C2 were found in 24 of the 29 (83%) patients compared with 18 of the 42 (43%) normal controls. HLA-DR3 was present in 20 (69%) of the patients and seven out of 39 (18%) of the normal controls. There was strong linkage disequilibrium between DR3 and the null alleles for C4A and C4B.The data did not permit the relative contributions of DR3 and null factors of C4A and C4B as genetic risk factors to be distinguished. The Al, B5, B7, B8, DR2, and DR3. The importance of these associations remains uncertain, but one possibility is that they reflect linkage disequilibrium with other loci that determine risk factors. In this context the HLA region encoded complement polymorphisms C2, C4A, C4B, and Bf may be relevant candidates. The polymorphism is particularly complex and extensive for the C4A and B loci.5 In addition to the expressed polymorphic variations null (silent) alleles for C2 and both C4 loci have been described," 8 and these are associated with no detectable product. Furthermore, variation in haemolytic activity between the C4 gene products has been observed, and one, C4A6, is nonhaemolytic when inherited in certain haplotypes. 9 Proved complement deficiency states account for only a small minority of cases of systemic lupus erythematosus, but no

Results appear to justify the continued use of volunteer donors in chronic-phase chronic myeloid leukemia, but infection and chronic GVHD are still major problems.