Failure of CD1D -/- Mice to Elicit Hypersensitive Granulomas to Mycobacterial Cord Factor Trehalose 6,6′-Dimycolate

Abstract

The present study defines pathologic differences in acute and hypersensitive responses to Mycobacterium tuberculosis glycolipid trehalose-6,6′-dimycolate (TDM, cord factor) in normal BALB/c mice and those deficient in group II CD1 molecule CD1d1. Mice immunized against TDM demonstrate hypersensitive responses, yet the mechanisms for TDM presentation remain elusive. Mice lacking CD1d (CD1D^-/-) demonstrate dysregulated granulomatous response to TDM, compared with CD1D^+/- heterozygous controls. Because CD1d-restricted T cells can regulate macrophage immune functions at mucosal surfaces, we hypothesized that CD1D^-/- mice would show deficient TDM-induced hypersensitive pulmonary granulomatous response in which T cells play a central role. Control CD1D^+/+ mice sensitized and subsequently challenged with TDM demonstrated aggressive inflammation defined by monocytic lesions contained by CD3⁺ lymphocytic cuffing. CD1D^-/- mice demonstrated distinctly different pathologies, with edema present concurrent with extended, nonfocal mononuclear cell-based granulomatous reactions. Furthermore, CD1D^-/- mice did not demonstrate destructive lesions, and CD3⁺ lymphocytes were only loosely organized in proximity to reactive pathology. The CD1d-deficient mice demonstrated rapid increases in proinflammatory mRNAs, with significant differences in interferon-γ(IFN-γ) compared to the wild-type group. IFN-γ, interleukin-6 (IL-6), and IL-12 proteins were significantly elevated in the CD1D^-/- group compared with wild-type mice(p < 0.05) 2 days after TDM challenge. However, by 7 days postadministration, similar production for all cytokines and proinflammatory molecules examined was present in both groups of mice. These experiments provide evidence for a role for CD1d in mediation of pathology during hypersensitive responses to the mycobacterial glycolipid TDM.