Cellular infiltration at skin lesions and draining lymph nodes of sheep infested with adult Hyalomma anatolicum anatolicum ticks.

Immunohistochemical analysis of skin and draining lymph nodes of sheep repeatedly infested with the ixodid tick Hyalomma anatolicum anatolicum were studied for different antigen-presenting cells and lymphocyte subpopulations. Infiltration of neutrophils, macrophages and lymphocytes adjacent to the tick bite site were observed. Skin biopsies showed significant increases in dermal infiltration of CD8+ and gammadelta+ T cells at 72 h and 8 days after both primary and secondary infestation. Infiltrations of MHC-II DR/DQ decreased at 72 h after tick infestation, whereas significant increases were recorded for 8-day skin biopsies. CD1+ cellular infiltrations were observed during secondary infestations at the dermis. Decreased ratios of CD4:CD8 T cells and MHC-II:CD1 antigen-presenting cells were observed in both infestations compared to healthy skin biopsies. Ratios of alphabeta:gammadelta T cells increased gradually during infestation compared to uninfested skin. The regional lymph nodes from tick-infested sheep showed an increased CD8+, gammadelta+ T and CD1+ cellular infiltration compared to control lymph nodes. CD4+ T cells were decreased. There were no significant changes in CD45R+ cellular infiltration either at skin lesions or regional lymph nodes.