CD4 and infection: Therefore, to determine if bovine γδ T cells that were protective in our co-culture system could protect in an in vivo model, Rag-1−/− mice were depleted of NK cells and reconstituted with bovine macrophages alone, macrophages plus autologous γδ T cells, or macrophages plus autologous CD4+ T cells prior to infection with B. abortus.