FUNCTIONAL AND MORPHOLOGICAL OBSERVATIONS ON THE EFFECT OF CYCLOPHOSPHAMIDE ON THE IMMUNE RESPONSE OF THE CHICKEN

Abstract

Summary The functional and morphological effects of cyclophosphamide (Cy) on the immune response of the chicken were investigated. Chickens given Cy on clays 1, 2 and 4 after hatching failed to produce antibody for at least 6 weeks and had low levels of serum IgG. Birds surviving for more than 6 weeks recovered their immunocompetence. The effect of Cy on cell‐mediated immunity (CMI) was less persistent. Allogeneic skin grafts applied to one‐week‐old treated birds were not rejected but grafts were rejected from 3‐week‐old recipients. At no time was graft versus host activity completely eliminated by Cy treatment. Morphological changes in the lymphoid organs reflected the results of functional tests. Early after treatment, lymphocytes were eliminated from thymus, bursa and spleen. Lymphoid regeneration usually occurred in the thymus by 3 weeks after treatment. Bursal regeneration was observed less frequently, and usually only in birds older than 6 weeks. In many birds, chronic degenerative changes in the epithelial cells were apparent, especially in the bursa. It was speculated that in those birds where thymus or bursa regeneration failed to occur there was damage to the epithelial component of the organs. Possibly the bursal epithelial cells were more susceptible to the action of Cy than were thymic epithelial cells.