B1a Lymphocytes (CD19+CD5+) Deficiency in Patients with Crohn's Disease and Its Relation with Disease Severity.

BACKGROUND/AIMS: B1a cells (CD19+CD5+) are considered elements of the innate immune system. The aim of this study was to evaluate the frequency of B1a cells in the peripheral blood of patients with Crohn's disease (CD) and its relation with disease severity. METHODS: In this prospective study, a total of 128 subjects (64 CD patients and 64 healthy controls) were studied. B1a cells in peripheral blood, CD Activity Index, and Simple Endoscopic Score of B1a cells were studied. RESULTS: A significant decrease of B1a cells in peripheral blood was observed in patients with CD versus controls (p = 0.002), especially in perforating or penetrating patterns (p = 0.017). A lower frequency of B1a cells is related to increased endoscopic severity (Spearman's Rho: -0.559, p = 0.004). The mean frequency of B1a cells in patients with pre- and post-study surgery was significantly lower than that in patients who did not undergo surgery (p = 0.050 and p = 0.026, respectively). CONCLUSIONS: The B1a cell count in peripheral blood is lower in CD patients. This decrease is directly related to the severity of the disease (penetrating or perforating, Simple Endoscopy Score and surgery complication). These results pointed to the fact that B1a cells play an important role in immune protection in CD.