Abstract
Purpose:
To characterize the ocular immune response to intravenous muramyl dipeptide (MDP) adjuvant.
Methods:
Adult rabbits were injected intravenously with MDP (1 mg/kg). Ocular exams, tear fluid collection and Schirmer’s tear test were performed through 48 h. Tear production, total tear protein, western blots for IgA and IgG, immunofluorescence antibody (IFA) detection of gamma-glutamyl transpeptidase (GGT; cellular marker for PMN), calreticulin (CRT, MDP binding protein) and Nod2 (intracellular ligand for MDP), GGT activity and tear cytology (H&E staining) were determined.
Results:
Clinical signs of uveitis and mild conjunctivitis were detected, but tear production, total tear protein and IgA/G levels were only slightly increased. The number of leukocytes in tear fluid and levels of GGT activity on Schirmer’s tear test strips were significantly higher (P's<0.01) than pre-treatment control levels at 12-48h post intravenous MDP. Serum GGT levels peaked at 24 h. Immunofluorescent staining of cellular infiltrate in tears revealed numerous leukocytes, predominantly heterophils (PMN) positive for GGT, calreticulin (CRT) and Nod2.
Conclusions:
The results suggest intravenous MDP induces inflammatory changes in the conjunctiva tissues and that the increase in GGT activity in the tear fluid at 16-48 h post intravenous MDP is likely due to Nod2, CRT, and GGT-positive heterophils.
Keywords: 475 conjunctivitis •
555 immunomodulation/immunoregulation •
433 bacterial disease