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Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California 94143;
World Health Organization Immunology Research and Training Center, Institute of Biochemistry, University of Lausanne, Epalinges CH-1066, Switzerland; || Cytel Corporation, San Diego, California 92121; and the ¶ Institute of Molecular and Cellular Pharmacology, University of Nice, Valbonne 06560, France
Experimental leishmaniasis offers a well characterized model of T helper type 1 cell (Th1)-mediated control of infection by an intracellular organism. Susceptible BALB/c mice aberrantly develop Th2 cells in response to infection and are unable to control parasite dissemination. The early CD4+ T cell response in these mice is oligoclonal and reflects the expansion of Vβ4/ V
8-bearing T cells in response to a single epitope from the parasite Leishmania homologue of mammalian RACK1 (LACK) antigen. Interleukin 4 (IL-4) generated by these cells is believed to direct the subsequent Th2 response. We used T cells from T cell receptor–transgenic mice expressing such a Vβ4/V
8 receptor to characterize altered peptide ligands with similar affinity for I-Ad. Such altered ligands failed to activate IL-4 production from transgenic LACK-specific T cells or following injection into BALB/c mice. Pretreatment of susceptible mice with altered peptide ligands substantially altered the course of subsequent infection. The ability to confer a healer phenotype on otherwise susceptible mice using altered peptides that differed by a single amino acid suggests limited diversity in the endogenous T cell repertoire recognizing this antigen.
Key Words: Leishmania major CD4+ T cell subsets altered peptide ligands LACK antigen
S. Pingel and P. Launois contributed equally to this work.
Abbreviations used: ABLE, LACK T cell receptor–specific transgenic; CDR3, complementarity determining region 3; LACK, Leishmania homologue of mammalian RACK1; RT, reverse transcriptase; TCR-C
0, T cell receptor constant region-
–deficient.
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