Effects of per anum immunization with sheep red blood cells on the structure of the post-capillary venules in the T-cell area of chicken cloacal bursa.

The experiment was designed to assess morphometrically the effects of per anum immunization with sheep red blood cells (SRBC; the response requiring participation of helper T cells), as measured by serum anti-SRBC agglutination titres, on the structure of the post-capillary venules (PCV) found in the diffusely infiltrated area (DIA) of the chicken cloacal bursa. Dpcv, the diameter of the PCV, increased from the control values of 18.725 and 17.159 microns to 24.564 and 25.062 microns following SRBC administration for 1 and 2 weeks, respectively. Migration index (MI) also significantly increased from 1.003 and 1.207 in controls to 1.686 and 1.718 in immunized animals, as did the endothelial cell height, Hend, from 5.767 and 5.660 microns to 8.833 and 9.540 microns during 1 and 2 weeks of SRBC immunization, respectively. These values were in direct relation to the anti-SRBC titres in serum. The findings are discussed in the light of local T-cell response, and conclusion was drawn that DIA must represent a T-cell region in the bursa, thus advocating further assessment of this organ with regard to its functions as a peripheral lymphatic organ as well.