Id. Haidl et al., DETECTION OF RESTRICTED ISOFORM EXPRESSION AND TYROSINE PHOSPHATASE-ACTIVITY OF CD45 IN MURINE DENDRITIC CELLS, European Journal of Immunology, 25(12), 1995, pp. 3370-3374
CD45 is a cell surface transmembrane tyrosine phosphatase. It is expre
ssed as distinct protein isoforms via alternative splicing of exons 4,
5 and 6. In T and B lymphocytes, CD45 is thought to play a critical r
ole in antigen-dependent signaling through their respective antigen re
ceptor complexes. However, the isoform expression and enzymatic activi
ty of CD45 in other leukocytes remains largely unknown. Here, we exami
ne the isoform expression and phosphatase activity of CD45 in murine d
endritic cells (DC). Flow cytometric double-labeling analysis and bioc
hemical analysis of purified splenic DC CD45 demonstrate that DC expre
ss both the CD45RB and CD45R0 isoforms. Flow cytometric analyses of fr
eshly isolated splenic DC and thymic DC also indicate the expression o
f CD45RB and CD45R0 on these DC populations. In addition, we find that
purified splenic DC CD45 possesses a high level of intrinsic tyrosine
phosphatase activity. These data therefore establish the restricted i
soform expression pattern of CD45 in murine DC and demonstrate that ce
lls lacking specific antigen receptor complexes have active tyrosine p
hosphatase activity associated with CD45.