Physical and molecular genetic analysis of Qa-2 antigen expression: multiple factors controlling cell surface levels.
We have examined the surface expression of Qa-2 on lymphocyte subpopulations and on splenocytes from inbred mouse strains by a radioactive binding assay using purified anti-Qa-2 antibodies and antibody fragments (Fab). Quantitative measurements by Scatchard analysis revealed that spleen cells from Qa-2high mice express (4-5) x 10(4) Qa-2 molecules/cell, whereas T lymphocytes have as high as (7-8) x 10(4) molecules/cell. In addition, it was determined that B lymphocytes express (5-6) x 10(3) molecules on their cell surface. The Qa-2 levels on anti-CD3-activated T cells is 1.0 x 10(5) molecules/cell. Previous experiments have shown that the quantity of Qa-2 varies in a strain-specific fashion and may be classified into three groups: Qa-2high, Qa-2medium and Qa-2low. Our results indicated that Qa-2high strains express (4-5) x 10(4) Qa-2 molecules/cell, Qa-2medium strains (B6-K2, B10.A, A/J, BALB/c and DBA/2) express (1-1.7) x 10(4) molecules/cell, and Qa-2low strains (SWR/J and DBA/1) express no more than 6 x 10(3) molecules/cell. Detection of Q7 or Q9 mRNA by the polymerase chain reaction revealed that Qa-2high strains express two functional Qa-2 enconding genes, Q7 and Q9, whereas Qa-2medium and Qa-2low strains express either Q7 or Q9. These results strongly suggest that Qa-2 gene dosage contributes in part to the variation of Qa-2 levels on the cell surface.
Tian
H
H
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Imani
F
F
Soloski
M J
MJ
D000818:Animals; D002478:Cells, Cultured; D002874:Chromosome Mapping; D005434:Flow Cytometry; D015870:Gene Expression; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000235:genetics; D007128:Immunoglobulin Fragments; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D016133:Polymerase Chain Reaction; D012313:RNA / Q000032:analysis; D013154:Spleen / Q000276:immunology; D014158:Transcription, Genetic
D015395:Histocompatibility Antigens Class I; D007128:Immunoglobulin Fragments; C032907:Q surface antigens; D012313:RNA