Immunosuppressive Effects of Lymphoproliferative Neoplasms of Chickens

Abstract

of natural antibody pioneered experimental studies on immunosuppression in tumor systems. It became apparent that hosts bearing progressive malignant disease usually had reduced immunocompetence. Stutman (43) recently reviewed the results of a vast number of experimental studies on the immunosuppressive effect of neoplasia. In the present report, I will discuss some of the information on the effects of Marek's disease (MD), lymphoid leukosis (LL), and reticuloendotheliosis (RE) on the immune competence of chickens. Because some of the earlier data on the subject have been reviewed previously (13,34), this paper emphasizes data that have appeared within the last few years. Marek's disease and LL are the two principal virus-induced malignant lymphoproliferative diseases that occur naturally in chickens. Marek's disease is caused by a herpesvirus that is highly contagious and spreads readily to susceptible chickens through a contaminated environment. Marek's disease is not transmitted vertically (42). It causes the transformation of T-cells in chickens and initiates vigorous humoral and cell-mediated immune responses to virus and tumor-associated antigens. Although the principal terminal lesion in MD is lymphoid cell proliferation, there is initially a severe depletion of lymphocytes in the major lymphoid organs: thymus, bursa, and spleen (35). The lymphoid depletion is probably associated with the lytic infection of lymphocytes with MDV. Lymphoid leukosis, on the other hand, is caused by a group of RNA viruses that are characteristically egg-transmitted and cause gross lymphomas in chickens, usually after a long latent period. The target cells for LL viruses are the B-cells resident in