EIMERIA-TENELLA - SPOROZOITES RARELY ENTER LEUKOCYTES IN THE CECAL EPITHELIUM OF THE CHICKEN (GALLUS-DOMESTICUS)

In this study, the intraepithelial leukocytes supposedly involved in t he transportation of Eimeria tenella sporozoites through the cecal lam ina propria were phenotypically characterized. The ceca of naive and i mmune chickens were examined at various times after inoculation by lig ht microscopy and immunocytochemical techniques. The distribution of s porozoites within the villus differed markedly between both groups. Fr om 16 hr postinoculation, significantly fewer sporozoites had reached the crypts in immune chickens, and schizont formation was inhibited. I n the villus epithelium of both naive and immune chickens, few sporozo ites were found within a leukocyte. Using anti-sporozoite and anti-CD4 5 monoclonals, we showed that even when intraepithelial leukocytes are abundantly present, only a few sporozoites were inside them. In the l amina propria of immune chickens significantly more sporozoites were f ound within leukocytes than in the lamina propria of naive chickens. T he phenotype of the few leukocytes that harbored sporozoites was simil ar in naive and immune chickens. A few sporozoites were detected in B cells, 10% in macrophages, and 50% in T cells, especially CD8(+) cells . These results show that E. tenella sporozoites rarely enter intraepi thelial leukocytes and therefore their putative role in transporting s porozoites through the lamina propria is doubtful. (C) 1995 Academic P ress. Inc.