1Wafaa A. Zahran, 1Mabrouk M. Ghonaim, 1Bothina
A. Koura, 1Hassan El-Banna, 1Sahar M. Ali and 2Nabila
El-Sheikh
1Microbiology & Immunology department,
Faculty of Medicine,
One third of the world’s population is infected with Mycobacterium
tuberculosis (MTB). However, active disease can develop only in a small
percentage, when the immunity is weakened. The acquired immune response to MTB
is primarily mediated by T cells. Natural killer (NK) cells play a central role
in innate immunity to microbial pathogens. Human NKT cells have characteristics
of both T and NK cells and also exhibit antimycobacterial activity. This work
aimed to enumerate T, NK and NKT cells in active pulmonary TB compared with
healthy controls and to study the correlation between these cells with different
factors affecting prognosis of pulmonary TB as disease severity, complications
or associated diseases, antitubrculosis chemotherapy, and age & gender. Of
the 22 active tuberculosis patients examined, 17 were recent cases and 5
recurrent. Healthy controls were divided into 14 individuals with detectable
reaction to purified protein derivative (PPD+) and 14 individuals without
detectable reaction to PPD-. The percentages of T, NK and NKT cells in
erythrocyte-lysed whole blood samples were determined using flowcytometry. The
percentage of NKT cells was significantly higher among the recently diagnosed
MTB cases as compared with both PPD+ (P<0.01) and PPD- (P<0.01) healthy
controls, while no significant difference could be found in the percentages of
T or NK cells among these groups. However, comparing recurrent cases with
recently diagnosed cases showed a significant difference only in the percentage
of T cells (P<0.01). There was also a significant difference in the
percentage of T cells according to severity of disease (P<0.01) and in the
association of diabetes mellitus (P<0.01). Age, gender and treatment with
antituberculosis chemotherapy had no effect on the percentages of T, NK or NKT
cells. It is concluded that T and NKT cells play an important role in immunity
against TB. In active pulmonary tuberculosis, increased T cell count points to
severity of the disease, while their reduced count predicts bad prognosis.
Human NKT cell count is a marker of disease activity. Enumeration of these
cells in peripheral blood can be used as a non-invasive prognostic indicator
for patients with active pulmonary TB.