Identification of an <i>Ixodes ricinus</i> salivary gland fraction through its ability to stimulate CD4 T cells present in BALB/c mice lymph nodes draining the tick fixation site

BALB/c mice infested with larvae or nymphs of <i>Ixodes ricinus</i> develop in their lymph nodes a T cell-specific immune response triggered by salivary gland soluble antigens (SGA). SGA are apparently conserved in the 3 biological stages of <i>I. ricinus</i> ticks and are species specific. SGA derived from partially fed females <i>I. ricinus</i> stimulate lymph node T cells from mice infested with <i>I. ricinus</i> larvae or nymphs. In contrast, lymph node cells from mice infested with <i>Amblyomma hebraeum</i> nymphs do not respond. A chromatographic fraction enriched with a 65 kDa protein (IrSG65) isolated from salivary glands of <i>I. ricinus</i> partially fed females induces in vitro a specific T cell proliferation of lymph node cells from mice infested with <i>I. ricinus</i> nymphs. The depletion of CD4+ T cells drastically reduces the ability of lymphocytes from infested mice to proliferate after IrSG65 stimulation.