Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/27/1999
Publication Date: N/A
Technical Abstract: This study evaluated changes in lymphocyte sub-populations in the ileal mucosa and draining lymph nodes of calves infected and challenged with Cryptosporidium parvum. Calves were divided in 5 groups: group 1 - uninfected, killed at 25 days of age (DOA), group 2 - infected at 18 DOA, killed at 21 DOA, group 3 - infected at 1 DOA, challenged at 18 DOA, killed at 21 DOA, group 4 - infected at 18 DOA, killed at 30 DOA. After challenge groups 3 and 5 did not shed oocysts, indicating that primary infection stimulated protection against reinfection. The most prominent immunological changes were in the intraephitelial lymphocytes (IEL), where there was an increase in the percentage of CD8+ lymphocytes, and a smaller increase in the percentage pf CD4+ lymphocytes. These increases were only seen in calves after a secondary infection (groups 3 and 5), and in calves killed 12 days after a primary infection (group 4). In contrast, the percentages of T cell subpopulations in calves 3 days after a primary infection (group 2) were similar to that of uninfected animals (group 1). Conversely, in mesenteric or ileo-cecal lymph nodes there was an increase of the percentage of CD4+ T cells 3 days after a challenge (group 3), suggesting a priming of lymphocytes in the lymph nodes followed by migration to and multiplication in the epithelium.