Effects of anti-macrophage serum on immunological reactivity and on the T cell area of the cloacal bursa in the chicken.

The effects of rabbit anti-chicken macrophage serum (RACMS) on the immune response in chickens stimulated locally with sheep red-blood cells (SRBC; T cell-dependent antigen) were studied, and the morphological alterations in the diffusely infiltrated area (DIA; T cell region of the bursa) were measured morphometrically. The response to SRBC was very significantly impaired in locally immunized chickens treated systemically with RACMS. In the DIA, systemic treatment with RACMS dramatically decreased the relative number of MPS cells (p less than 0.001). Local administration of RACMS, in turn, caused pronounced morphological changes in the PCVs of the DIA: decrease in the diameter of the PCV and its lumen, due to the flattening of the endothelial cells. A highly significant decline in the migration index was observed as well. This study confirms the important function of MPS cells in a T-dependent immune response and further suggests that circulating MPS cells, like T and B lymphocytes, may use the PCVs as route of migration from blood to lymphatic tissue.