Production of human monoclonal antibodies to i blood group by EBV-induced transformation: possible presence of a new glycolipid in cord red cell membranes and human hematopoietic cell lines.
To study the differentiation-associated glycolipid two anti-i mAb producers, GL-1 and GL-2, were established from the combination of EBV-induced transformation of normal PBL and immune lysis of fluorescent dye-trapped liposome-containing bovine i-active glycolipid. The mAb GL-1 reacted with both sialosylparagloboside and pentahexosyl ceramide and the bovine i-active glycolipid whereas mAb GL-2 reacted only with the bovine i-active glycolipid in LILA. Both mAbs cold-agglutinate human cord red cells but not adult red cells. However, unexpectedly, the majority of the reactivity of these mAbs in human cord red cells on TLC was not identical to the i-active glycolipid. The GL-1 antigenic substance is considered to be a glycolipid distinct from the i-active glycolipid because the immunoreactivity was canceled with endoglycoceramidase which cleaves a linkage between the oligosaccharide and ceramide. Based on complement cytolysis with the mAb, 15 hematopoietic cell lines and normal peripheral lymphocytes were screened for susceptibility to the mAbs. A Burkitt lymphoma cell line, Ramos, was most sensitive among those tested, and BJA-B, Daudi, Namalwa in the B cell lines, TALL-1, Jurkatt in the T-cell lines and HL-60 in the non-lymphoid cell lines were sensitive whereas normal lymphocytes or other 8 cell lines were not. An immunoreactive spot with the same Rf with cord red cells was also detected in sensitive cell lines. The possible presence of a new glycolipid antigen determined from the mAb and related to the differentiation of hematopoietic cells was speculated.