CD4 and infection: Since depletion of either CD4+ or CD8+ T cells by themselves did not promote the level of systemic relapse observed with cyclophosphamide treatment over the time period analyzed (Fig. 2 and 3), our results therefore suggest either that both lymphocyte subtypes are able to contribute to suppression of chronic-stage infections in the colon or that innate monocytes/macrophages are able to provide a covering role during this period.