The role of bursa-dependent responses in immunity to infectious laryngotracheitis.

The effect of combined day-old surgical bursectomy and cyclophosphamide therapy on the response of young chicks to Brucella abortus antigen and cloacal vaccination against infectious laryngotracheitis virus (ILTV) was examined. The combined treatment effectively prevented the development of serum antibody to both B abortus and ILTV, yet when these chickens were challenged with virulent ILTV, they were found to be immune. It is suggested that immunity to ILTV may depend on the development of a cell mediated immune response.