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

The immunological mechanisms that lead to the control of Mycobacterium tuberculosis infection are not well known.

To study the role of lymphocyte subsets and co-stimulatory molecules in M. tuberculosis infection.

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, alphabetaTCR and gammadeltaTCR), 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.

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).

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.