Eimeria tenellaInfection Induces Local Gamma Interferon Production and Intestinal Lymphocyte Subpopulation Changes

Abstract

The role of intestinal lymphocytes and gamma interferon (IFN-␥) production in protective immunity to Eimeria tenella infection was evaluated in two inbred strains of chickens (SC and TK) that display different patterns of susceptibility to coccidiosis. Oral inoculation of either strain with E. tenella led to parasite invasion of the intestinal cecum and cecal tonsils. Greater fecal oocyst shedding was seen in TK chickens. Flow cytometric analyses of cecal tonsil lymphocytes demonstrated greater numbers of CD4؉ and T-cell receptor ␥␦-positive (TCR1 ؉ ) cells in SC chickens and elevated numbers of CD8 ؉ and TCR2 ؉ cells in TK chickens following primary infection. IFN-␥ mRNA expression was significantly increased in cecal tonsil and intraepithelial lymphocytes at days 6 and 8, respectively, after primary infection in SC compared to TK chickens. While no differences were noted between cecal tonsil lymphocytes of the two strains following secondary infection, TK chickens showed elevated IFN-␥ transcript levels in intestinal intraepithelial lymphocytes at this time. Selective depletion of CD4؉ , but not CD8 ؉ , cecal tonsil lymphocytes in SC chickens resulted in a reduced IFN-␥ mRNA expression, indicating that CD4؉ cells are the primary source of this cytokine. Collectively, these results indicate that local lymphocyte responses and production of IFN-␥ are influenced by host genetic factors.Apicomplexan protozoa of the genus Eimeria are a common cause of coccidiosis. Following ingestion of infective oocysts, coccidial parasites undergo a complex life cycle ultimately impairing the gastrointestinal tract and resulting in nutrient malabsorption, body weight loss, and in severe cases, death (13). Cell-mediated immunity (CMI) plays a major role in host protection against coccidiosis in chickens (3, 27, 32) and mice (36,49). Alterations in lymphocyte subpopulations and cytokine production during Eimeria infections in both animals have been investigated to clarify the nature of protective immunity (2,12,25). These studies have shown that gamma interferon (IFN-␥) is an important component of the host protective CMI (7, 26). Chicken IFN-␥ has been cloned (9,19,41,48), and monoclonal antibodies (MAbs) against the recombinant protein have been used to further characterize CMI during coccidiosis (50).Different species of Eimeria are known to display tissue tropism within the avian intestinal tract. For example, E. tenella primarily infects the cecum and cecal tonsils located at the ileocecal junction, which contain the major source of lymphocytes in the cecum. It was therefore of interest to examine the roles of lymphocyte subpopulations and IFN-␥ production in the cecal tonsils of chickens infected with E. tenella. To perform these studies, we took advantage of the fact that genetically divergent, inbred strains of chickens, SC (B 2 B 2 ) and TK (B 15 B 21 ), display different degrees of susceptibility to E. tenella infection. SC chickens consistently produce fewer fecal oocysts than TK chickens following E. tenella infection. ...

Effects of dietary conjugated linoleic acid on the duodenal mucosal immunity response and redox status of broiler chicks infected with Eimeria aceruvlina

“…In this experiment, dietary CLA did not change the percentage of duodenal CD4 + T lymphocytes and simultaneously had no effect on IFNγ expression, which is consistent with the viewpoint of Yun et al (2000). However, Laurent et al (2001) found that the IFNγ from CD8 + T lymphocytes was directly involved in the cellular immune response against coccidiosis in the test of broiler chicks infected with Eimeria tenella and Eimeria maxima.…”

“…During the Eimeria tenella infection, the depletion of CD4 + T lymphocytes in the cecal tonsil of broiler chicks suppressed the IFNγ expression, while the depletion of CD8 + T lymphocytes enhanced the IFNγ expression, which is why Yun et al (2000) considered that IFNγ was derived from CD4 + T lymphocytes. In this experiment, dietary CLA did not change the percentage of duodenal CD4 + T lymphocytes and simultaneously had no effect on IFNγ expression, which is consistent with the viewpoint of Yun et al (2000).…”

Immunological basis of differences in disease resistance in the chicken

“…There is a correlation between resistance to these diseases and early and higher IFN-γ production. A high level of IFN-γ production has also been shown in chicken strains that are resistant to coccidiosis [20,90,139]. These observations suggest that chicken lines with an enhanced IFN-γ response are more resistant to some viral and parasitic infections.…”

“…Similarly, a CD4 + cell dominated mucosal T cell response has been reported in chicken strains resistant to coccidiosis, whereas the susceptible lines have abundant CD8 + cells in the gut-associated lymphatic tissue [85,139]. In contrast, a CD8 + T cell biased response is predominant in chickens that are resistant to salmonella infection and have higher response to vaccination [10].…”

“…The different sub-populations of the αβ T cells, such as those differentiated by the V region of the chain, Vβ1 + (TCR2) or Vβ2 + (TCR3) [75], or by the accessory receptor molecules CD4 + or CD8 + [92], have distinct functional activities [3,26]. The amount and proportion of the T cell sub-populations in blood and in peripheral tissues have been correlated with differences in disease susceptibility [135,139]. Quantitative and/or qualitative alterations in T cells sub-population could influence immune competence and resistance differences against infectious pathogens and certain autoimmune diseases such as scleroderma [135] and thyroiditis [27].…”