Circulating γδ T Cells in Response to Salmonella enterica Serovar Enteritidis Exposure in Chickens
Berndt, Angela | Pieper, Jana | Methner, U (Ulrich)
γδT cells are considered crucial to the outcome of various infectiousdiseases. The present study was undertaken to characterizeγδ (T-cell receptor 1⁺[TCR1⁺]) T cells phenotypically and functionally inavian immune response. Day-old chicks were orally immunized withSalmonella enterica serovar Enteritidis live vaccine or S.enterica serovar Enteritidis wild-type strain and infected usingthe S. enterica serovar Enteritidis wild-type strain on day 44of life. Between days 3 and 71, peripheral blood was examined flowcytometrically for the occurrence of γδ T-cellsubpopulations differentiated by the expression of T-cell antigens.Three different TCR1⁺ cell populations were found todisplay considerable variation regarding CD8α antigenexpression: (i) CD8α⁺highTCR1⁺ cells, (ii)CD8α⁺dim TCR1⁺ cells, and(iii) CD8α⁻ TCR1⁺ cells.While most of the CD8α⁺highTCR1⁺ cells expressed the CD8αβheterodimeric antigen, the majority of theCD8α⁺dim TCR1⁺ cells werefound to express the CD8αα homodimeric form. Afterimmunization, a significant increase ofCD8αα⁺high γδ Tcells was observed within the CD8α⁺highTCR1⁺ cell population. Quantitative reversetranscription-PCR revealed reduced interleukin-7 receptor α(IL-7Rα) and Bcl-x expression and elevated IL-2Rα mRNAexpression of the CD8αα⁺highγδ T cells. Immunohistochemical analysis demonstrated asignificant increase of CD8α⁺ andTCR1⁺ cells in the cecum and spleen and a decreasedpercentage of CD8β⁺ T cells in the spleenafter Salmonella immunization. After infection of immunizedanimals, immune reactions were restricted to intestinal tissue. Thestudy showed that Salmonella immunization of very young chicksis accompanied by an increase ofCD8αα⁺high γδ Tcells in peripheral blood, which are probably activated, and thusrepresent an important factor for the development of a protectiveimmune response to Salmonella organisms inchickens.
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