Mycobacterium tuberculosis bacteria are rapidly phagocytosed by alveolar macrophages when introduced into the lung. However, the bacteria are able to block degradation pathways within the macrophages and resist killing by RNS and ROS that the macrophages produce, leading to chronic infection. Despite the persistent infection, the macrophages are still able to produce IL-12 and TNF-a which will eventually lead to recruitment of T-helper cells to the site of infection. (4 pts)

1. Which type of T-helper effector cells would be recruited to the lung?

2. What would the role of the T-helper cell be at the site of infection?

3. Should this lead to clearance of the infection?

4. What happens if the bacteria are not cleared?