부산대학교 도서관

The 180000 MW isoform of CD45 (CD45RO) has been identified in cattle with a novel monoclonal antibody (mAb) (IL-A116). This has allowed a more precise analysis of T-cell function in relation to CD45 isoform expression. Within the CD44 and CD8+ T-cell populations, CD45RO+ and CD45RO- subsets were evident. Most CD4+ and CD8- T cells that expressed the CD45RO isoform did not express the 220000 and 205000 MW isoforms recognized by mAb CC76. In contrast, the WCI +, CD2-, CD4-, CD8+, γδ T-cell receptor (TCR)+ T cells in bovine peripheral blood mononuclear cells (PBMC) were all CD45RO+. Monocytes and granulocytes were CD45RO+ but B cells were CD45RO+. Sorting experiments with CD4+ T cells from an immunized calf demonstrated that proliferative responses to ovalbumin (OVA) were entirely within the CD45RO+ subset. Following stimulation with concanavalin A (Con A) the CD45RO- subset of CD4+ T cells produced transcripts for interleukin-2 (IL-2) but not IL-4 or interferon-γ (IFN-γ), while the CD45R0+ subset produced mRNA for IL-2, IL-4 and IFN-γ. Biologically active IL-2 was present in supernatants from both CD45RO+ and CD45RO-, CD4+ T cells, and IFN-γ protein was identified by ELISA in supernatants from the CD45RO+ subset, confirming the production of cytokines implied by polymerase chain reaction (PCR). In contrast, sorting experiments with CD8+ T cells from animals immune to the protozoan parasite Theileriaparva revealed substantial numbers of cytotoxic T-lymphocyte precursors in both the CD45RO+ and CD45RO- subsets. Thus it appears that although all antigenically primed CD4+ T cells remain CD45RO+, and expression of this molecule consequently identifies memory cells within PBMC, antigenically primed CD8+ T cells down-regulate CD45RO expression after activation. [ABSTRACT FROM AUTHOR]