Immunohistoiogical analysis of leukocyte subsets in gut tissue at different times after C. parvum in calves was performed to identify the host effector cells recruited to the infected tissues. At 72 hr post-infection (pi), a significant mobilization of conventional a/$ T cells (CD4 and CDS T cells) and y/8 T cells was seen within the lamina propria and Payer's patch of the ileal sections shown to be infected with C. parvum. Similar analysis on immune animals following a challenge infection revealed a large increase in the populations of CD4 and CDS T cells, but not f/S T cells, in specific regions of the ileum of challenged animals. Interestingly, a significant number of CDS T cells were intimately associated with epithelial cells in the ileum of the challenged animal. This was not observed in infected tissues of control immune or naive animals. Analysis of the expression of vascular adhesion molecules potentially involved in the recruitment of leukocytes to the infected tissues revealed that expression of the peripheral lymph node vascular addressin (PNAd) is induced on vessels within the lamina propria and Peyer's patch of the infected ileum. To directly examine the physiological relevance of PNAd expression in response to C. parvum infection, we blocked the interaction between PNAd and lymphocytes using mAbs in vivo. Staining revealed that the tissues were heavily infected with C. parvum, however, no increase in the population of CD4, CDS or y/8 T cells was seen. We are currently determining the effect of blocking PNAd on the severity and outcome of disease in experimentally infected calves.
|Original language||English (US)|
|State||Published - Dec 1 1996|