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Published on: July 11, 2015
Interleukin-2 production by mitogen-stimulated intestinal mucosal leukocytes from cattle
1Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, Canada.
Insights
Cattle intestinal leukocytes produce interleukin-2 (IL-2) when stimulated with mitogens like concanavalin A (conA). This immune response is influenced by accessory cells and indomethacin, highlighting T-cell involvement in gut immunity.
Area of Science:
- Veterinary Immunology
- Gastrointestinal Immunology
- Cellular Immunology
Background:
- The small intestine harbors diverse leukocyte populations crucial for immune surveillance.
- Interleukin-2 (IL-2) is a key cytokine for T-cell proliferation and function.
- Understanding bovine intestinal immune cell responses is vital for animal health.
Purpose of the Study:
- To investigate the capacity of bovine intestinal leukocytes to produce IL-2.
- To identify mitogens that stimulate IL-2 production in different leukocyte subsets.
- To characterize factors influencing IL-2 production in the bovine gut.
Main Methods:
- Isolation of leukocytes from intraepithelial, lamina propria, and aggregated lymphatic follicles of cattle small intestine.
- In vitro stimulation of leukocyte populations with mitogens such as concanavalin A (conA), phytohemagglutinin, and pokeweed mitogen.
- Quantification of IL-2 activity in culture supernatants using an IL-2-dependent lymphoblastoid cell line.
- Assessment of the effects of indomethacin, 2-mercaptoethanol, phorbol myristate acetate, adherent cells, and Ia-positive accessory cells on IL-2 production.
Main Results:
- All three leukocyte populations (intraepithelial, lamina propria, aggregated lymphatic follicles) produced IL-2 upon stimulation with conA.
- IL-2 activity peaked between 30-50 hours post-stimulation and was detectable as early as 20 hours.
- ConA was the most potent mitogen for IL-2 induction across all leukocyte populations.
- Indomethacin enhanced conA-induced IL-2 production, while depletion of Ia-positive accessory cells inhibited it.
- IL-2 producing lymphocytes in aggregated lymphatic follicles were identified as T cells based on cell surface markers and functional assays.
Conclusions:
- Bovine intestinal leukocytes, particularly T cells, are capable of producing IL-2 in response to mitogenic stimulation.
- Accessory cells play a critical role in mediating IL-2 production.
- The findings provide insights into the cellular mechanisms of gut-associated immunity in cattle.
Abstract:
Leukocytes isolated from intraepithelium, lamina propria, and aggregated lymphatic follicles of the small intestine of healthy adult cattle were tested for their ability to produce interleukin 2 (IL-2) by in vitro stimulation of cells with mitogens. Supernatants from interepithelial leukocytes, lamina propria leukocytes, and cultures stimulated with concanavalin A (conA), phytohemagglutinin, and pokeweed mitogen contained growth factors with the capacity to maintain proliferation of a bovine IL-2-dependent lymphoblastoid cell line. Interleukin-2 activity was demonstrated in supernatants of all 3 conA-stimulated leukocyte populations as early as 20 hours after initiation of culture, reached peak values at 30 to 50 hours, and decreased by 72 hours. Although quantitative variations of IL-2 production were observed between various cell types and among cattle, conA was the most potent in inducing IL-2 activity in all 3 leukocyte populations. Supplementation of culture medium with 2-mercaptoethanol or phorbol myristrate acetate neither induced IL-2 production nor enhanced mitogen-induced IL-2 production. Addition of indomethacin to conA-stimulated cultures enhanced IL-2 production. Although depletion of adherent cells did not affect IL-2 production, total elimination of Ia-positive accessory cells inhibited its production by all 3 cell populations. Lymphocytes responsible for IL-2 production in aggregated lymphatic follicle population were presumptive T cells because they were nylon wool-nonadherent, B26A positive (monoclonal antibody directed against pan T cells), pIg45A negative (antibody directed against pan B cells), and considered peanut agglutination-positive.
