Two Alpha Chains and Three Beta Chains of Human Ia Antigens
Human Ia antigens, structural and serologic analogues of murine Ia antigens, are composed of two polypeptide chains, α (34,000 MW) and β (28,000 MW). Like their murine counterparts, these polymorphic chains transiently associate with a third, invariant chain, Ii (31,000 MW) (1). These readily apparent similarities with the mouse raise questions about the genetic organization of the HLA-D region which codes for human Ia antigens. Its murine analog, the I region in the H-2 complex, is known to contain at least five genes whose products have been characterized either biochemically or serologically. In particular, two distinct populations of murine Ia antigens, I-A and I-E/C, have been analyzed and shown to be coded by two separate I region genes (2). In the past, studies based on family data and serology using conventional alloantisera indicated a considerable molecular diversity of the human Ia antigens. Development of hybridoma technology (3) and monoclonal anti-la antibodies provided specific reagents with which to try to isolate various species of human Ia antigens.
KeywordsAlpha Chain Beta Chain Invariant Chain Homozygous Cell Line Human Genetic Mutant Cell Repository
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