Tumour necrosis factor B gene polymorphism in relation to complotype in couples with spontaneous abortions and in control families.

NcoI restriction fragment length polymorphism (RFLP) of the tumour necrosis factor B (TNFB) gene gives two allelic fragments of 5.5 and 10.5 kb, corresponding to the TNFB*1 and TNFB*2 alleles, respectively. The frequencies of these alleles were analysed in 121 healthy Finns and 56 Finnish couples suffering from recurrent spontaneous abortions (RSA). In the healthy Finns the frequency of TNFB*1 was 37% and that of TNFB*2 63%, of which the frequency of TNFB*1 was significantly increased compared with the Danish population. No deviation was seen between the RSA couples and the Finnish controls. TNF genes are located in major histocompatibility complex class III region close to complement (BF, C4A and C4B) genes. Some complotypes associated most often with the TNFB*1 (S01, S30, S02) and some (S31, F320) with the TNFB*2 allele in the healthy Finns. The combination of the TNFB and the C4 'null' allele differed between the RSA couples and the Finnish controls.