Induction of Ly-6A/E expression by murine lymphocytes after in vivo immunization is strictly dependent upon the action of IFN-α/β and /or IFN-γ

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Abstract
Ly-6A/E Is a phosphpatidylinositol-linked membrane protein which mediates murine T and B cell signalling. IFN-γ, IFB-α/β, LPS, and IL-4 have all been reported to induce or upregulate Ly-6A/E by normal lymphocytes. Since no systematic study has addressed the stimulant selectivity of Ly-6A/E expression by murine lymphocytes nor investigated its Induction and regulation during primary in vivo immune responses we analyzed in vitro Ly-6A/E expression after multiple stimuli and during a number of distinct in vivo Immunizations. We show that LPS induces B cell Ly-6A/E in vitro by stimulating the release of IFN-α/β by ‘contaminating’ adherent cells. In the presence of anti-IFN-γ + anti-IFN-α/β antibodies, no Ly-6A/E was Induced upon addition of multiple cytokines, Including IL-4, or mitogenic doses of anti-lg antibody. Furthermore, IFN-γ-containing, CD4+ T cell (Th1) supernatants potently induced Ly-6A/E by murine B cells whereas IL-4-containing (Th2) supernatants were either weak or ineffective; anti-IFN-γ + anti-IFN-α/β Inhibited Ly-6A/E induction by both Th1 and Th2 supernatants. Immunization of mice with Brucella abortus or poly (I)-poly (C) resulted In Induction of Ly-6A/E expression by virtually all B and T cells, whereas Injection of GαMδ led to peak induction of Ly-6A/E by ∼50% of both B and T cells. Lymphocytes from mice infected with the nematode parasites Nippostrongylus brasillensis or Heligmosomoides polygyrus expressed no Ly-6A/E. Injection of mice with anti-IFN-γ and/or anti-IFN-α/β antibodies at the time of immunization abrogates Ly-6A/E Induction in all model systems tested. These results indicate that Ly-6A/E is a highly selective, If not exclusive, marker of in vitro and in vivo IFN action and may thus play a role in cell-mediated immune responses.

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