Research article

CXCL10⁺ T cells and NK cells assist in the recruitment and activation of CXCR3⁺ and CXCL11⁺ leukocytes during Mycobacteria-enhanced colitis

Udai P Singh¹ , Rajesh Singh² , Shailesh Singh² , Russell K Karls³ , Frederick D Quinn³ , Dennis D Taub⁴ and James W Lillard Jr^1,2

¹Department of Microbiology, Biochemistry, & Immunology, Morehouse School of Medicine, Atlanta, GA, USA

²Department of Microbiology & Immunology, University of Louisville, Louisville, KY, USA

³Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, USA

⁴Laboratory of Immunology, National Institute of Aging, Gerontology Research Center, Baltimore, MD, USA

author email corresponding author email

BMC Immunology 2008, 9:25doi:10.1186/1471-2172-9-25

Published:	4 June 2008

Abstract

Background

The role of Mycobacteria in the etiology of Crohn's disease (CD) has been a contentious subject for many years. Recently, our laboratory showed that spontaneous colitis in IL-10^-/- mice is driven in part by antigens (Ags) conserved in Mycobacteria. The present study dissects some of the common cellular and molecular mechanism that drive Mycobacteria-mediated and spontaneous colitis in IL-10^-/- mice.

Results

We show that serum from inflammatory bowel disease (IBD) patients contain significantly higher levels of Mycobacterium avium paratuberculosis-specific IgG1 and IgG2 antibodies (Abs), serum amyloid A (SAA) as well as CXCR3 ligands than serum from healthy donors. To study the cellular mechanisms of Mycobacteria-associated colitis, pathogen-free IL-10^-/- mice were given heat-killed or live M. avium paratuberculosis. The numbers of mucosal T cells, neutrophils, NK/NKT cells that expressed TNFα, IFN-γ, and/or CXCL10 were significantly higher in mice that received live Mycobacteria than other groups. The numbers of mucosal CXCR3⁺, CXCL9⁺, CXCL11⁺ and/or IFN-γ⁺ dendritic cells (DCs) were also significantly higher in M. avium paratuberculosis-challenged mice, than compared to control mice.

Conclusion

The present study shows that CD and UC patients mount significant Mycobacteria-specific IgG1 > IgG2 and CXCR3 ligand responses. Several cellular mechanisms that drive spontaneous colitis also mediate Mycobacteria-enhanced colitis in IL-10^-/- mice. Similar to IL-10^-/- mice under conventional housing, we show that Mycobacteria-challenge IL-10^-/- mice housed under otherwise pathogen-free conditions develop colitis that is driven by CXCR3- and CXCR3 ligand-expressing leukocytes, which underscores another important hallmark and molecular mechanism of colitis. Together, the data show that Mycobacteria-dependent host responses, namely CXCL10⁺ T cells and NK cells, assist in the recruitment and activation of CXCR3⁺ and CXCL11⁺ leukocytes to enhance colitis of susceptible hosts.