Activating natural killer (NK) cytotoxicity of canine CD5(-) CD21(-) cells requires low surface CD5 density NK cells

作者：Lin C. S.; Chang C. P.; Chiang H. C.; Chuang T. F.; Hsu C. H.; Liu C. C.^*

来源：Iranian Journal of Veterinary Research, 2018, 19(2): 87-95.

• CD5(-) CD21(-)cells
• Cytotoxicity
• Low surface CD5 density
• Natural killer cells

Natural killer (NK) cells play a crucial role in regulating immune functions. Few studies have characterized canine NK cells. We previously demonstrated that canine peripheral blood lymphocytes (PBLs) with a low surface CD5 density (CD5lo) are considered a critical NK population. Natural killer cells in most mammals do not express T-cell markers, but canine CD5l0 cells express surface molecules, such as CD3 T-cell receptors. These features make canines unique models for the study of comparative immunology in NK cells. In this study, we discovered that CD5l0 and CD21(-) double-negative (CD5l0-ne/CD2(-)) cells were originally low in NK cytotoxicity and their NK cytotoxicity was highly activated when co-cultured with CD5l0 NK cells. The cytotoxicity was not activated when co-cultured with other cell types, such as high surface CD5 density (CD5hi) cells. The CD5l0-negative (CD5l0-ne) population comprises CD5(-) and CD5hi cells. CD5-cells were low in NK cytotoxicity initially or after culturing with interleukin-2 (IL-2) without CD5l0 cells; however, the addition of CD5l0 cells in a similar medium markedly enhanced the NK activity. By contrast, CD5hi cells were always NK inactive, irrespective of them being cultured with CD5l0 cells or not. We further verified that only the CD5 CD21cells, which were separated from CD5(-) CD21(+) cells in the entire CD5(-) population, showed activated NK activity through CD5l0 cell induction. This study is the first to reveal that canine NK cells enhanced NK-inert cells to become NK-cytotoxic cells. Additionally, it is concluded that in beagles, except for CD5l0 cells, CD5(-) CD21(-)cells show NK activity.

• 出版日期2018