Functional Dysregulation of PBMC and PMN in Crohn's Disease

Aim: We evaluated the cellular response of polymorphonuclear leukocytes (PMN) and peripheral blood mononuclear cells (PBMC) against viable Mycobacterium avium subspecies paratuberculosis (MAP) for possible understanding of the role of MAP in the pathogenesis of Crohn's disease (CD) patients. Methods: In vitro phagocytosis and cell proliferation with the aid of Confocal Scanning Laser Microscopy (CSLM) were used to evaluate the immunogenicity of PMN and PBMC freshly obtained from 19 CD patients and 11 healthy controls against viable human-strain MAP, MAP antigens, and Phytohematoagglutonin (PHA), a suspect in CD pathogenesis. Results: MAP DNA was detected in tissue from 15/17(88%) CD subjects, 1/2(50%) UC patients and not in blood samples from 11 healthy controls. PMN phagocytosis was suppressed in 13/19 CD subjects (68%) compared to none in controls (p< 0.001); suppression ranged from 6 to 97%. PBMC phagocytosis was suppressed only in 5/19 (26%) of CD subjects; suppression ranged between 1 to 70%. PMN-specific plasma inhibitors were detected in 9/19 (47%) CD subjects compared to none in controls (P<0.05). Plasma inhibitors specific to PBMC phagocytosis were mildly present in CD patients (3/19 (16%) CD subjects) compared to none in controls. All 13 (68%) CD subjects that have suppressed PMN phagocytosis were also positive for MAP DNA detection in tissue. PBMC from 8/19 (42%) CD subjects showed dysfunctional proliferative response against PHA (ranged between 1 to 82%) compared to 1 healthy control, suggesting possible T-cell anergy. Out of PBMC from the 11 CD subject's that reacted normally to PHA, 7 reacted strongly to MAP PPD; suggesting pre-exposure to Mycobacteria.. Of 11 healthy control subjects, 10 (91%) reacted normally to PHA. Conclusions: It is possible that MAP may directly or indirectly exacerbate a pre-existing defect in phagocyte function - or it may cause the dysfunction employing similar molecular mechanisms used by other pathogenic mycobacteria like M. leprae and M. tuberculosis. Collectively the data supports a mycobacterial role in some CD patients.