Gluten-reactive CD4+ T cells, activation

In the intestinal mucosa of celiac disease patients, gluten-specific CD4+ T cells recognize gliadin antigens, particularly those deamidated by the tissue transglutaminase enzyme (TG2) (Lundin et al., 1993; Arentz-Hansen et al., 2000). These antigens are presented by antigen-presenting cells (APCs) expressing HLA-DQ2 or HLA-DQ8 molecules (Arentz-Hansen et al., 2000; Broughton et al., 2012). Antigen presentation activates the gluten-specific CD4+ T cells, initiating a cascade of immune responses.

Upon activation, gluten-specific CD4+ T cells undergo rapid clonal expansion and differentiation into a pro-inflammatory population that secretes cytokines such as interferon-gamma (IFNγ) and tumor necrosis factor-alpha (TNFα) (Nilsen et al., 1998). Additionally, B cells with B cell receptors (BCRs) specific for TG2-gliadin complexes can present these complexes to gluten-specific CD4+ T cells, further stimulating their activation (Di Niro et al., 2012).

The release of IFNγ upregulates the expression of HLA class II molecules on APCs, enhancing the efficiency of gluten peptide presentation (Meresse et al., 2006). This creates a feedback loop that amplifies antigen presentation and intensifies the T cell-mediated immune response to gluten.

• Isolation from Intestinal Biopsies: Gluten-reactive T cells can be isolated from patients with celiac disease but not from healthy controls.
• T Cell Activation Measured by Phenotyping: Activated T cells, specifically CD25+ (expressing the IL-2 receptor α-chain), can be identified through phenotyping. When small intestinal biopsies from celiac disease patients on a gluten-free diet are challenged ex vivo with gluten, CD4+ T cells in the lamina propria become activated and express CD25 (Lundin et al., 1993).
• Proliferation Assays: Proliferation assays are performed using antigen-presenting cells (APCs), specific peptides or digested gliadin, and T cells labeled with a marker such as tritiated thymidine (³H). After incubation, plates are harvested, and the incorporation of ³H is measured to assess T cell proliferation (Arentz-Hansen et al., 2000, Broughton et al., 2012, Fallang et al., 2009).
• In Vitro T/B-Cell Cooperation Assay: T/B-cell cooperation is assessed by culturing A20 B-cells with TCR transfectants in the presence of various complexes and conditions. Murine IL-2 secretion, a marker of T cell activation, is measured by ELISA as the readout (Di Niro et al., 2012).
• Additional Applications of ELISA: ELISA is also used to quantify cytokines in biopsies, providing insights into immune responses (Nilsen et al., 1998).
• Quantification of Cytokine mRNA Expression: Competitive PCR is employed to compare cytokine production at the mRNA level. mRNA is reverse-transcribed, amplified by PCR, and visualized on agarose gels. Band intensities are analyzed to determine the ratios of cytokine expression (Nilsen et al., 1998).

Homo sapiens

• Arentz-Hansen H, Körner R, Molberg Ø, Quarsten H, Vader W, Kooy YMC, Lundin KEA, Koning F, Roepstorff P, Sollid LM, McAdam S. (2000). The intestinal T cell response to α-gliadin in adult celiac disease is focused on a single deamidated glutamine targeted by tissue transglutaminase. J Exp Med. 191:603-612.

• Broughton SE, Petersen J, Theodossis A, Scally SW, Loh KL, Thompson A, van Bergen J, Kooy-Winkelaar Y, Henderson KN, Beddoe T, Tye-Din JA, Mannering SI, Purcell AW, McCluskey J, Anderson RP, Koning F, Reid HH, Rossjohn J. (2012). Biased T cell receptor usage directed against human leukocyte antigen DQ8-restricted gliadin peptides is associated with celiac disease. Immunity. 37:611-621.

• Di Niro R, Mesin L, Zheng NY, Stamnaes J, Morrissey M, Lee JH, Huang M, Iversen R, du Pré MF, Qiao SW, Lundin KE, Wilson PC, Sollid LM. (2012). High abundance of plasma cells secreting transglutaminase 2-specific IgA autoantibodies with limited somatic hypermutation in celiac disease intestinal lesions. Nat Med. 18:441-445.

• Fallang LE, Bergseng E, Hotta K, Berg-Larsen A, Kim CY, Sollid LM. (2009). Differences in the risk of celiac disease associated with HLA-DQ2.5 or HLA-DQ2.2 are related to sustained gluten antigen presentation. Nat Immunol. 10:1096-1101.

• Lundin KE, Scott H, Hansen T, Paulsen G, Halstensen TS, Fausa O, Thorsby E, Sollid LM. (1993). Gliadin-specific, HLA-DQ(alpha 10501,beta 10201) restricted T cells isolated from the small intestinal mucosa of celiac disease patients. J Exp Med. 178:187-196.

• Meresse B, Curran SA, Ciszewski C, Orbelyan G, Setty M, Bhagat G, Lee L, Tretiakova M, Semrad C, Kistner E, Winchester RJ, Braud V, Lanier LL, Geraghty DE, Green PH, Guandalini S, Jabri B. Reprogramming of CTLs into natural killer-like cells in celiac disease. J Exp Med 2006;203:1343-1355. 

• Molberg Ø, Kett K, Scott H, Thorsby E, Sollid LM, Lundin KE. (1997). Gliadin specific, HLA DQ2-restricted T cells are commonly found in small intestinal biopsies from coeliac disease patients, but not from controls. Scand J Immunol. 46:103-109.

• Molberg Ø, McAdam SN, Körner R, Quarsten H, Kristiansen C, Madsen L, Fugger L, Scott H, Noren O, Roepstorff P, Lundin KE, Sjöström H, Sollid LM. (1998). Tissue transglutaminase selectively modifies gliadin peptides that are recognized by gut-derived T cells in celiac disease. Nat Med. 4:713-717.

• Nilsen EM, Jahnsen FL, Lundin KE, Johansen FE, Fausa O, Sollid LM, Jahnsen J, Scott H, Brandtzaeg P. (1998). Gluten induces an intestinal cytokine response strongly dominated by interferon gamma in patients with celiac disease. Gastroenterology. 115:551-563.