Tissue Non-specific Alkaline Phosphatase Expression Is Needed for the Full Stimulation of Lymphocytes

Intestinal and tissue non-specific alkaline phosphatase (IAP and TNAP) are coexpressed in mouse colon, and the latter predominates in inflammatory conditions. It has been described that IAP dephosphorylates LPS and as a result prevents chemically induced colitis and metabolic syndrome. Because experimental colitis is differentially induced in TNAP+/- and wild type TNAP +/+ mice (TNAP -/- mice die early after birth), we hypothesized that TNAP is involved in T cell activation. In order to explore this hypothesis, primary splenocytes and T lymphocytes isolated by negative magnetic separation were obtained from WT and TNAP+/- C57BL/6J mice and stimulated in vitro with concanavalin A. We also stimulated lymphocytes in vivo with anti-CD3 antibody (50 μg/mouse i.p.). Cytokine production in primary splenocytes and cytokine plasma levels were studied. Cytokines were assessed by ELISA. Cells from TNAP+/- (with severely reduced TNAP expression) mice produced lower amounts of IFNg, IL-17 and IL-1β in response to concanavalin A. Stimulation of TNAP+/- with anti-CD3 resulted in lower (45%) plasmatic TNFα levels and a decreased production of IFNg (28%) by splenocytes ex vivo. These results show that the lack of a TNAP allele hampers cytokine response and indicate a role for this enzyme in the immune response.