Scarcity of gamma delta T cells in intestinal epithelia containing coccidia despite general increase of epithelial lymphocytes

Ruminant Coccidiosis

Ruminant coccidiosis, caused by Eimeria species, is a significant and widespread enteric disease in young livestock worldwide. High morbidities and significant mortalities may be observed. For disease diagnosis, fecal samples from clinically ill animals should be analyzed for both, identity (ie, pathogenicity) of Eimeria species and excreted oocyst amount. To prevent coccidiosis-related economic losses, management measures to reduce infection pressure and improve general animal health are crucial. Anticoccidial drugs are widely used to control clinical and subclinical disease. Treatment is most efficient when applied prophylactically or metaphylactically. To avoid development of parasite drug resistance, drugs should be used sustainably.

Treatment of mice with the anticoccidial drug Toltrazuril does not interfere with the development of a specific cellular intestinal immune response to Eimeria falciformis

Immunity against Eimeria-infections is highly specific and it depends on cell-mediated effector mechanisms. Infections of BALB/c mice with 1,000 sporulated oocysts of Eimeria falciformis led to protection against challenge infections. Treatment with the anti-coccidium Toltrazuril, during primary infection, terminated the ongoing disease and did not interfere with the establishment of protective immunity against challenge infections. Mesenteric lymph node cells of infected, treated as well as non-treated and challenged BALB/c mice, showed a similar proliferation upon stimulation with parasite antigen. In contrast, neither cells of the Peyer's patches, intraepithelial lymphocytes, nor spleen cells responded to stimulation with parasite antigens. Cells from all compartments and of all investigated groups proliferated and released the cytokines IFN-gamma and IL-4 in response to the mitogen Concanavalin A. The number of cells releasing IFN-gamma or IL-4 was not dependent on the status of infection or previous treatment with Toltrazuril. The serum IgG response against total sporozoite antigens of individual mice showed that in addition, a systemic humoral response developed in infected mice, independent of a previous drug treatment, although the specific IgG antibody concentration was higher in non-treated mice. Thus, Toltrazuril does not impair the parasite specific intestinal cellular and systemic antibody response and does not prevent the development of protection against challenge infection.

Lymphoid follicles of different phenotype appear in ileum during involution of the sheep ileal Peyer's patch

The ileal Peyer's patch (IPP) of young sheep is a site of diversification of the primary antibody repertoire and where involution takes place at young age. Tissue samples from the ileum were collected in 134 animals aged from 1 month to 6 years, and IPP follicle phenotypes were characterised. We describe a new type of ileal lymphoid follicles that became relatively more frequent during involution, and had numerous intrafollicular T-cells and BAQ44A+ B-cells and large interfollicular T-cell areas. As opposed to classical IPP follicles in which the BAQ44A+ cells were confined to the narrow follicle-neck region, the novel atypical ileal lymphoid follicle had these cells distributed throughout the follicle. The relative distribution of cell types in the typical IPP follicle remained fairly constant during involution. Many animals older than 9 months (64/92) still had had typical IPP follicles and even sheep 4 years and older (5/9) had IPP-type follicles.

Lymphocyte depletion in ileal Peyer's patch follicles in lambs infected with Eimeria ovinoidalis

A total of 14 lambs were experimentally infected with Eimeria ovinoidalis in two separate experiments in two consecutive years. Nine lambs served as uninoculated controls. Material was collected from the ileum 2 weeks after infection in eight lambs and 3 weeks after infection in six lambs. Lambs examined 2 weeks after infection had normal follicles. After three weeks, the follicle-associated epithelium covering the lymphoid follicles of the ileal Peyer's patches showed fusions with adjacent absorptive epithelium, focal hyperplasia, and occasionally necrosis. Macrogametes, microgamonts, and oocysts were often found in the follicle-associated epithelium and the dome region. Various degrees of lymphocyte depletion were present in the ileal lymphoid follicles in all six infected lambs 3 weeks after infection, and four lambs had decreased follicle size. Reduced staining for leukocyte common antigen (CD45), B-cell markers, and the proliferation marker Ki-67 was present in these lambs. Application of the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling method for apoptotic cells revealed decreased staining in the ileal lymphoid follicles 3 weeks after infection. A marker of follicular dendritic cells, 5'- nucleotidase, showed increased reactivity, probably due to condensation of reticular cells following loss of follicle lymphocytes. Reduced staining for carbonic anhydrase in the follicle-associated epithelium and the domes was present in all six lambs examined 3 weeks after infection, indicating decreased production of carbonic anhydrase-reactive 50-nm particles and a decreased lymphoproliferative stimulus. In conclusion, the present study shows that severe E. ovinoidalis infection in lambs causes lesions of the follicle-associated epithelium and may result in lymphocyte depletion and atrophy of the ileal Peyer's patch follicles.

T cell responses in calves to a primary Eimeria bovis infection: phenotypical and functional changes

The study aimed to characterize T cell responses in calves to a primary E. bovis infection. For this purpose, peripheral blood lymphocytes (PBL) were isolated from six infected calves and three controls during prepatency (Day 12 post infection (p.i.), patency (Day 25 p.i.) and postpatency (Day 35 p.i.). In addition, lymphocytes were isolated from various lymphatic organs (lnn. cervicales superficiales, lnn. jejunales craniales, lnn. jejunales caudales, lnn. caecales, lnn. colici, Peyer's patches (PP) and spleen) at necropsy (Day 35 p.i.). FACS analyses determined the proportions of CD4+-, CD8+-, CD2+-, and gammadelta+-T cells. Proliferative responses of the cells after stimulation with Concanavalin A (Con A) and an E. bovis-merozoite I antigen (EbAg) were measured. Furthermore, in situ hybridization experiments were performed for the detection of IL-2 and IL-4 mRNA in histological sections of lymphatic organs. Proportions of CD4+-, CD8+- and CD2+-expressing PBL were significantly increased 12 days p.i. in infected calves. While the proportions of CD4+- and CD8+-PBL declined until day 25 p.i. and finally reached control values, proportions of activated PBL (CD2+-T cells) remained at a high level throughout the observation period. Those of gammadelta+-PBL, in contrast, remained unaffected. The proportions of CD4+-, gammadelta+- and CD2+-T cells in lymphatic organs were significantly increased in comparison to uninfected controls, when determined 35 days p.i. Concerning the proportions of CD8+-T cells of the organs, however, there were no differences between the groups. PBL and cells from lymphatic organs except those from the PP showed strong proliferative response to the mitogen Con A, without a significant difference between the groups. Reactions to EbAg in contrast differed significantly between controls and E. bovis infected calves. Proliferation responses of PBL of infected animals were highest 12 days p.i.; subsequently they decreased and 35 days p.i. they were found within the ranges of controls. Lymphocytes isolated from lymphatic organs of infected animals reacted significantly stronger than lymphocytes from control animals, whereby most marked differences occured with cells from lymph nodes draining E. bovis infested parts of the intestine and from the spleen. These reactions were accompained by an increased transcription of the IL-2 gene but not of the IL-4 gene in gut associated lymphnodes of infected calves when compared with infected controls. The data suggest strong antigenic stimuli by developing first generation schizonts, and of predominant involvement of (CD4+) Th1 cells in the course of a primary E. bovis infection of calves.

Prominence of gammadelta T cells in the elicitation phase of dinitrochlorobenzene-induced contact hypersensitivity in lambs

Immunohistochemical techniques were used to identify T-cell subpopulations in the ear skin of lambs during the elicitation phase of dinitrochlorobenzene (DCNB)-induced contact hypersensitivity. Thirty lambs (21-26 weeks of age) were divided into groups of 10. The shaved right ear of one group was treated with DNCB. Two weeks later, this group was challenged with DNCB. One group was treated with the vehicle alone, and the remaining group was left untreated. The lambs were killed 48 hours after challenge, and tissue specimens were collected from the ears of the three groups. There was an increase in T-cell populations in the skin of the DNCB-treated lambs 48 hours after challenge. The majority of the T cells were CD8+ and associated predominantly with the blood vessels and adnexa of the superficial dermis. There was also an increased presence of CD4+ cells and gammadelta T cells in the superficial dermis. In the epidermis, clusters of gammadelta T cells and CD4+ cells were associated with microlesions. Computer-assisted morphometric analysis was used to estimate the relative presence of the T-cell subpopulations in the superficial and deep dermis and the entire dermis. Statistical analysis of the relative area of immunostaining showed that the significant increases in all T-cell subpopulations (CD4+, CD8+, and gammadelta T cells) in the entire dermis were accounted for by changes in the superficial dermis. The prominence of gammadelta T cells in delayed-type hypersensitivity in the skin of domestic ruminants has been the subject of conflicting reports. In the present study, CD4+ cell and gammadelta T-cell populations were of similar size in the normal and DNCB-treated lambs, suggesting an equal participation in the elicitation phase of contact hypersensitivity.

Isolation and phenotypic characterization of abomasal mucosal lymphocytes in the course of a primary Ostertagia ostertagi infection in calves

Isolation and characterization of surface marker phenotypes of abomasal intraepithelial (IEL), lamina propria (LPL) and abomasal lymph node lymphocytes (ABLN) from uninfected calves were conducted, and the dynamics of change in these populations during the course of a primary Ostertagia ostertagi infection were defined. To obtain viable IEL and LPL from the abomasal mucosa of cattle, a modified isolation method was developed. The phenotypic characterization of abomasal lymphocytes was accomplished by indirect immunofluorescence staining. In uninfected animals, numbers of T cells exceeded the number of immunoglobulin-bearing cells in IEL, LPL and ABLN. The predominant T cell type in IEL and LPL was CD8+ cells, while the CD4+ T cell predominated in ABLN. Levels of activated cells and T cell receptor-1 gamma delta T cells were higher in IEL and LPL compared to ABLN. Within 3 weeks of infection, the number of lymphocytes recovered from the abomasal lamina propira and the mass of the ABLN was dramatically increased when compared to uninfected animals. Laser flow cytometric analysis demonstrated increased levels of immunoglobulin-bearing cells, gamma delta T cells, and activated T cells in IEL, LPL and ABLN in the infected animals. The greatest changes in LPL and ABLN took place during the first days of infection, and these changes were apparent throughout the 28 days covered by the experiment.

T cell subsets and Langerhans cells in the forestomach mucosa of adult sheep and sheep foetuses

As part of a study on leukocytes in the ruminant forestomach the occurrence and distribution of T cells and major histocompatibility complex Class II positive (MHC-II+) cells in the forestomach mucosa of sheep were investigated. Samples were taken from the reticulum, atrium ruminis, ventral rumen, dorsal rumen and omasum of five healthy adult ewes and seven nearly fullborne foetuses. Frozen sections were stained with an indirect immunoperoxidase method using monoclonal antibodies against sheep MHC-II, CD4 and CD8 molecules and the sheep gamma delta T cell receptor. Both MHC-II+ cells and T cells were distributed along the basal lamina of the epithelium, with either mainly intraepithelial (CD8+ and gamma delta +cells) or mainly subepithelial (MHC-II+ and CD4+ cells) location. The MHC-II+ cells showed dendritic morphology and were interpreted as Langerhans cells. In adults ewes CD4+T cells comprised the major T cell subset at all sample sites. The number of T cells declined from the atrium ruminis through the ventral rumen to the dorsal rumen, while the number of Langerhans cells showed no marked variation between different sample sites. In foetuses, Langerhans cells showed a relatively high prevalence, while T cells were sparse and showed a more random distribution in the rumen wall. No marked variation between sample sites were observed in the fetal forestomachs. It is concluded that Langerhans cells and T cells are normally present in the forestomach mucosa of sheep, and it is suggested that the Langerhans cells represent a constituent component, while the prevalence and distribution of T cells may be influenced by antigen leakage through the epithelium.