B-lymphocytes and co-stimulatory molecules in Mycobacterium tuberculosis infection

SETTING: The immunological mechanisms that lead to the control of Mycobacterium tuberculosis infection are not well known. OBJECTIVE: To study the role of lymphocyte subsets and co-stimulatory molecules in M. tuberculosis infection. DESIGN: In 35 patients with pulmonary tuberculosis (PTB) and their contacts, 29 persons with tuberculin skin test conversion (TSTC) and 20 healthy individuals with negative tuberculin skin test (NTST), we studied T-lymphocyte subsets (CD3, CD4, CD8, αβTCR and γδTCR), B-cells, monocytes and co-stimulatory molecules CD28 and CD86 in peripheral blood. The results were analysed at univariate and multivariate level through discriminant analysis. RESULTS: At univariate level, compared with TSTC and NTST, PTB patients presented a decrease in CD4+ T-cells (P = 0.002), and B-cells (P = 0. 02 and 0.001, respectively). With regard to NTST subjects, PTB patients also showed a decrease in the percentage of CD86+ monocytes (P = 0.02) and an increase in the percentage of CD86+ B-lymphocytes (P = 0.02). At multivariate level, CD4+ T-lymphocytes showed statistical differences between PTB and TSTC subjects (P = 0.001). B-lymphocytes were discriminant between PTB and NTST (P < 0.001) and between TSTC and NTST individuals (P = 0.01). CONCLUSION: The number of total CD4+ T-cells is the best discriminant parameter for distinguishing between disease and infection, whereas the B-cell count is the best between healthy and infected individuals.