CD4 and infection: Mixed breed dogs infected experimentally with E. canis and monitored for 4 months post infection had no significant changes in the concentration of serum IgG, IgM and IgA, the percentage of circulating CD4+ T cells or the in-vitro function of blood lymphocytes (as determined by mitogen stimulation and the ability of lymphokine-activated killer cells to cause lysis of a 51Cr-labelled target monocyte cell line).