二株单克隆抗体识别人类由不同位点编码的类Ia抗原分子

用人的急性淋巴细胞白血病细胞株(Reh cell line)作免疫原,得到二株抗人的类Ia抗原单克隆抗体:H4和3A4。它们对带有类Ia 抗原的所有细胞都有补体依赖的细胞毒反应。二者免疫沉淀法试验结果也都表示它们识别的抗原是由分子量为 35 K和 28 K的 α链及β链组成。这和 Ia抗原一致。但在细胞毒滴度相同条件下,H4可明显抑制 MLC反应,而3A4无抑制作用,H4单克隆抗体的 F(ab’)_2 断片也对3A4的细胞毒无抑制作用。顺序免疫沉淀研究结果证明H4和3A4这二个单克隆抗体是和不同的抗原分子起反应,提示人类可能存在二种以上类Ia抗原,分别由不同的基因位点编码。从这二个单克隆抗体对 MLC抑制反应的不同,进一步推测 D和 DR基因可能也不相同。

THE RECOGNITION OF DIFFERENT MOLECULES OF HUMAN IA-LIKE ANTIGENS BY TWO MONOCLONAL ANTIBODIES

Two anti-la monoclonal antibodies, H4 and 3A4, were produced from the same fusion using a human ALL cell line Reh as immunogen cells. They both had complement-dependent cytotoxicity to all la positive cells tested and could immunoprecipitate molecular weight of 35K and 28K antigens which conformed the characteristics of la-like antigens. Monoclonal antibody H4 inhibited MLR strongly, however, 3A4 did not at the same condition of cytotoxic titer. In addition, F(ab')2 fragment from H4 could not block the cytotoxicity of A4 to the target cells. The results of sequential immunoprecipitation indicated that the antigens recognized by these two monoclonal antibodies were of different molecules. All of these observations suggest that there may be at least two kinds of human la-like antigens which are encoded by separate loci in MHC. From the results of the different inhibition of two monoclonal antibodies to MLR it seems to show that D and DR loci in MHC are probably different.