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Mycobacterium tuberculosis-induced activation accelerates apoptosis in peripheral blood neutrophils from patients
Mercedes Alemán1, Ana García, María A Saab
1Departamento de Inmunología, Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina, Buenos Aires, Argentina.
Abstract:
The activation of circulating polymorphonuclear neutrophils (PMN) from patients with active tuberculosis (TB-PMN) may be associated with induction of apoptosis. Spontaneous or Mycobacterium tuberculosis (MTB)-induced apoptosis of PMN were evaluated by microscopy, DNA content, and their binding to Annexin V at 0, 3, and 18 h. In addition, the expression of CD11b and of CD16 were evaluated as parameters of activation and apoptosis, respectively. Recently isolated TB-PMN showed a higher CD11b expression than normal PMN (N-PMN), but there were no features of apoptosis, even though an enhancement of Fas expression was observed. Spontaneous apoptosis was accelerated in TB-PMN at 3 h, but no differences were observed in TB- and N-PMN at 18 h of culture. When stimulated with MTB, both TB- and N-PMN steadily increased CD11b expression along the culture period. MTB induced apoptosis of N-PMN at 3 h with loss of CD16 expression. By contrast, MTB delayed the apoptotic rate of TB-PMN, preserving the CD16 receptor at 3 h, whereas it accelerated apoptosis at 18 h, increasing at the same time the expression of CD11b. Taken together, these data suggest that the acceleration of apoptosis observed in TB-PMN could be associated with the MTB-induced activation.
Insights
Polymorphonuclear neutrophils (PMN) in active tuberculosis (TB) patients show accelerated apoptosis. Mycobacterium tuberculosis (MTB) delays apoptosis in TB-PMN initially but accelerates it later, suggesting a link to MTB-induced activation.
Area of Science:
- Immunology
- Cell Biology
- Infectious Diseases
Background:
- Circulating polymorphonuclear neutrophils (PMN) play a role in the immune response to tuberculosis (TB).
- The behavior of PMN, including their activation and apoptosis, in patients with active TB requires further investigation.
Purpose of the Study:
- To investigate spontaneous and Mycobacterium tuberculosis (MTB)-induced apoptosis in PMN from active TB patients (TB-PMN).
- To compare TB-PMN with normal PMN (N-PMN) regarding activation and apoptosis markers.
Main Methods:
- PMN apoptosis evaluated by microscopy, DNA content, and Annexin V binding at 0, 3, and 18 hours.
- Expression of CD11b (activation marker) and CD16 (apoptosis marker) assessed.
- Stimulation with MTB was performed to assess its effect on PMN apoptosis and activation.
Main Results:
- Recently isolated TB-PMN exhibited higher CD11b expression than N-PMN without initial signs of apoptosis.
- Spontaneous apoptosis was accelerated in TB-PMN at 3 hours.
- MTB induced apoptosis in N-PMN but delayed it in TB-PMN at 3 hours, preserving CD16 expression.
- MTB accelerated TB-PMN apoptosis at 18 hours while increasing CD11b expression.
Conclusions:
- Accelerated apoptosis in TB-PMN may be linked to MTB-induced activation.
- Differential responses of TB-PMN and N-PMN to MTB suggest complex immune modulation in active tuberculosis.