Unreliability of the microcomplement fixation method for Xg(a) typing of cultured fibroblasts

Evidence pointing to localization of the Xg locus on either the long or short arm of the X chromosome is conflicting. Whether the Xg locus is subject to X-inactivation is also undecided. A report that Xga antigen could be detected on cultured fibroblasts or in hybridized cell lines by microcomplement fixation seemed to open new possibilities of studying these important problems. However, the results presented indicate that Xga typing of cultured fibroblasts cannot be done reliably by either the microcomplement fixation method described by Fellous et al. or by the authors' own absorption techniques. They attempted to obtain complement fixation using guinea pig complement as well as human complement because some blood-group antibodies are hemolytic in vitro only if heterologous complement is used. The problem of inconsistent typing resulting from the presence of heterophile antibodies in serum used as complement source has been discussed.