A novel CD45RA+CD4+ transient thymic subpopulation in MRL-lpr/lpr mice: its relation to non-proliferating CD4CD8CD45RA+ tumor cells

Abstract
MRL-lpr/lpr mice have hypertrophied lymph nodes comprising CD4CD8 T cells. In addition, they contain CD4+CD8 T cells co-expressing the CD45RA marker. The correlation between these two subpopulations has been difficult to assess. We analyzed the expression of CD45RA (with the RA3-2C2 antibody) In various thymic and peripheral T cell subsets, using three-color immunofluorescence. We showed that in lpr mice (i) a translent CD4+CD8 thymic subset co-expresses CD45RA during the course of the disease, and (ii) thymic as well as peripheral CD4CD8 and CD4+CD8 T cells brightly express CD45RA; furthermore (iii) in the lymph nodes, during lymphadenopathy, CD4+CD8CD45RA+ T cells show a broad range of the CD4 fluorescence intensity, and (iv) the increase in MHC class II expression is restricted to CD45RA T cells of the thymus and lymph nodes of lpr mice. Taken together, these data suggest that the CD4+CD8CD45RA+ population might generate the CD4CD8 tumor cells. In addition, using the bromodeoxyuridine labeling technique, we demonstrate that these cells are not the result of increased proliferation.

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