It is well documented that a number of bacterial, viral and parasitic infections decrease T-cell numbers through the apoptosis pathway.22 To determine whether apoptosis contributes to the loss of T cells, thymus organs were collected from mice to examine the expression of well-characterized apoptosis cell markers, including Annexin V, caspase-3, proapoptotic genes (GILZ, Bim, p53, Bax, Fas, and FasL), and antiapoptotic genes (Bcl2 and BCL-XL). The gene discussed is FAS; the disease is parasitic infectious disease.