Abstract
Human serum was found to contain a variety of class I-like molecules by Western blotting with anti-class I heavy chain reagents: major bands usually are observed around M r 44 000, 40 000, and 35 000–37 000. HLA-A24-positive individuals are distinguished by higher serum levels of M r 44 000 and 40 000 class I-like molecules than those found in HLA-A24-negative individuals. The M r 44 000 serum molecules are probably intact class I molecules that have been shed from the cell membrane, because they contain both a transmembrane segment (TM), as deduced from detergent-binding experiments, and a cytoplasmic tail (CT), as inferred from reactivity with an antipeptide serum specific for the cytoplasmic domain of class I antigens (RaCT). The M r 35 000 and 37 000 molecules contain neither a TM nor a CT region and therefore are probably proteolytic breakdown products of cellular and/or serum M r 44 000 molecules, although the existence of Q10-like molecules in man cannot be ruled out. The M r 40 000 molecules do not contain a TM region. M r 40 000 molecules reactive with the RaCT serum were found in the minority (2/13) of sera tested. We conclude that alternative splicing resulting in a precise excision of the TM exon plays a minor role in the generation of serum HLA class I antigens.
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Abbreviations
- B2m:
-
beta-2 microglobulin
- BSA:
-
bovine serum albumin
- EBV-BLCL:
-
Epstein-Barr virus-transformed B lymphoblastoid cell line
- mAb:
-
monoclonal antibody
- SDS-PAGE:
-
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- TCA:
-
trichloroacetic acid
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Dobbe, L.M.E., Stam, N.J., Neefjes, J.J. et al. Biochemical complexity of serum HLA class I molecules. Immunogenetics 27, 203–210 (1988). https://doi.org/10.1007/BF00346587
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DOI: https://doi.org/10.1007/BF00346587