EXPRESSION OF HRF20, A REGULATORY MOLECULE OF COMPLEMENT ACTIVATION, ON PERIPHERAL-BLOOD MONONUCLEAR-CELLS

  • 1 March 1990
    • journal article
    • research article
    • Vol. 69  (3) , 396-401
Abstract
HRF20 is a homologous restriction factor of 20,000 MW that prevents cells from membrane attack by homologous complement. HRF20 has been identified by a monoclonal antibody (mAb), 1F5, and is one of the phosphatidylinositol(PI)-anchored cell-surface glycoproteins. We analyzed the distribution of HRF20 expressed on subsets of peripheral blood lymphocytes using 1F5. HRF20 is expressed in relatively large amounts on T cells. In contrast, adherent cells possess smaller amounts of HRF20 while having large quantities of decay-accelerating factor (DAF). Although DAF was shown to be deficient or present at rather low levels on NK cells, HRF20 was detected in 95% of large granular lymphocytes (LGL), as described by FACS analysis. We also determined the effect of 1F5 on both mononuclear leukocytes and T cells in terms of their growth response. The results show that 1F5 induces T-cell proliferation when cells are stimulated with interleukin-2 (IL-2). In addition, induction of proliferation is facilitated by cross-linking 1F5 with a second antibody. These results suggest that HRF20 expressed on T cells not only protects them from cytotoxic attack by homologous complement, but also may initiate intracellular signals leading to cell activation when they happen to be cross-linked.

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