Identical expression of CD45R isoforms by CD45RC+ 'revertant' memory and CD45RC+ naive CD4 T cells.
Naive and memory CD4 T cells are frequently defined by exon-specific monoclonal antibodies (mAb) which stain (or not) high- or low-molecular-weight (MW) isoforms of the leucocyte common antigen CD45. The link between isoform and the naive/memory designation is complicated by the fact that CD4 T cells with a 'memory' phenotype (CD45RA-, RB-, RC-, or CD45RO+) may revert ('revertants') and re-express the high mw isoform (CD45RA+, RB+, RC+). Isoform expression also changes during normal T-cell development. Furthermore, the picture may be incomplete since an exon-specific mAb will not detect all possible isoforms on a cell. We have used molecular techniques to determine whether revertant CD4 memory T cells were different from naive T cells with respect to CD45R isoform expression. Using the anti-CD45RC mAb OX22 to purify rat lymphocyte subsets, CD45R isoform expression was examined at the mRNA level in CD4 T cells at different stages of development and compared with that of B cells and unseparated lymphocytes. B cells contained abundant message for the highest MW 3-exon isoform ABC, the 2-exon isoforms AB and BC, and the null isoform O. Both immature CD45RC- (i.e. CD4+8- 'single positive' thymocytes, and peripheral Thy-1+ recent thymic emigrants) and mature CD45RC- 'antigen-experienced' CD4 T cells had message for single-exons B, possibly C and for the O exon. In contrast, CD45RC+ CD4 T cells contained mRNA coding for ABC (low level), AB, BC, B, C (low level) and O (low level). Importantly, there was no difference between CD45RC+ T cells that had not seen antigen ('truly native') and CD45RC+ antigen-experienced revertant memory T cells. This observation has implications for understanding long-term immunological memory.
Hargreaves
M
M
Immunology Research Group, Medical School, University of Manchester, UK.
Bell
E B
EB
D000818:Animals; D016175:B-Lymphocyte Subsets / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D015870:Gene Expression; D007156:Immunologic Memory; D017493:Leukocyte Common Antigens / Q000032:analysis* / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D016176:T-Lymphocyte Subsets / Q000276:immunology*
D012333:RNA, Messenger; D017493:Leukocyte Common Antigens