Phenotypic analysis of peripheral B cell populations during Mycobacterium tuberculosis infection and disease

Mycobacterium tuberculosis (Mtb) remains an unresolved threat resulting in great annual loss of life. The role of B cells during the protective immunity to Mtb is still unclear. B cells have been described as effector cells in addition to their role as antibody producing cells during disease. Here we aim to identify and characterize the frequency of peripheral B-cell subpopulations during active Tuberculosis and over treatment response. Analysis were done for both class switched (CS) and non-class switched (NCS) phenotypes.

We recruited participants with active untreated pulmonary Tuberculosis, other lung diseases and healthy community controls. All groups were followed up for one week from recruitment and the TB cases till the end of treatment (month 6).

Peripheral blood samples were collected, stained with monoclonal antibodies to CD19(+) cells, Immunoglobulin (Ig) M, plasma cells (CD 138(+)), marker of memory (CD27(+)), immune activation (CD23(+)) and acquired on a flow cytometer. Circulating Marginal zone B cells (CD19(+)IgM(+)CD23(-)CD27(+)) and memory phenotypes are able to distinguish between TB diagnosis and end of treatment. The frequency of mature B cells from TB cases are lower than that of other-lung diseases at diagnosis. A subpopulation of activated memory B cells (CD19(+)IgM(+)CD23(+)CD27(+)) cells are present at the end of TB treatment.

This study identified distinctive B cell subpopulations present during active TB disease and other lung disease conditions. These cell populations warrants further examination in larger studies as it may be informative as cell markers or as effectors/regulators in TB disease or TB treatment response.