Monoclonal antibody LR-1 recognizes murine heat-stable antigen, a marker of antigen-presenting cells and developing hematopoietic cells.
The rat monoclonal antibody LR-1 was initially described to be reactive with an antigen present on murine splenic B lymphocytes. However, flow-cytometric analyses of cells obtained from thymus, bone marrow, spleen, and lymph nodes showed that LR-1 stained approximately 95, 95, 60-70 and 20% of cells present within these tissues in normal DBA/2 mice. The marker recognized by LR-1 was present on peripheral erythrocytes and splenic dendritic cells, and activation with lipopolysaccharide A further increased expression of this antigen by splenic B cells. This particular tissue and cellular distribution was similar to that delineated with monoclonal antibodies reactive with heat-stable antigen (HSA). Duallabelling studies were conducted to compare the reactivity patterns of LR-1 and the HSA-reactive monoclonal antibody J11d and indicated that both antibodies recognized splenocytes bearing B cell (IgM) or erythroid (TER-119, CD71) but not T cell (CD4, CD8) markers. Splenocytes exposed to phosphoinostol-specific phospholipase C showed marked reduction in LR-1 binding, indicating that this antibody recognized a glycosylphosphatidylinositol-anchored cell surface protein, consistent with the known structure of HSA. Mixing of LR-1 with the HSA-specific antibodies J11d or M1/69 provided flow-cytometric profiles indistinguishable from those obtained with either antibody alone. However, LR-1 inhibited M1/69 binding to splenocytes by 83%, while J11d reduced M1/69 binding to these cells by only 18%. This finding suggested that LR-1 and M1/69 recognize identical splenic HSA epitopes, while LR-1 and J11d bind distinct antigenic determinants of spleen HSA. Western blot analysis of splenocyte, thymocyte, bone marrow cell and erythrocyte detergent extracts revealed that LR-1 reacted with glycoforms of HSA of known molecular weights (30-55 kD). Thus, LR-1 recognizes HSA, the murine analogue of human CD24, and will be a useful reagent with which to investigate the role of HSA in the immune response and hematopoiesis.
Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada.
D W
DW
Hunt
H J
HJ
Jiang
D J
DJ
Granville
D E
DE
King
J G
JG
Levy
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000938:Antigen-Presenting Cells / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D015415:Biomarkers; D015153:Blotting, Western; D051927:CD24 Antigen; D003429:Cross Reactions / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology; D004912:Erythrocytes / Q000276:immunology; D005434:Flow Cytometry; D017261:Glycosylphosphatidylinositols; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins; D051379:Mice; D008811:Mice, Inbred DBA; D051381:Rats; D013047:Specific Pathogen-Free Organisms; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D010738:Type C Phospholipases / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015415:Biomarkers; D051927:CD24 Antigen; C497890:Cd24a protein, mouse; D017261:Glycosylphosphatidylinositols; D007075:Immunoglobulin M; D008562:Membrane Glycoproteins; D010738:Type C Phospholipases