If a person has numerous (>6) poorly demarcated lesions, what does this indicate about their immune response to Mycobacterium leprae?

The presence of numerous poorly demarcated lesions in an individual infected with Mycobacterium leprae indicates a selective inability to mount an adequate cellular immune response. This condition is often associated with lepromatous leprosy, which is characterized by a weak or absent cell-mediated immune response to the bacteria.

In lepromatous leprosy, the patient's immune system cannot effectively control the infection, resulting in the development of multiple lesions that are not well-defined. This occurs due to the failure of T-lymphocyte activation, which is critical for containing the Mycobacterium leprae. The inability to mount a robust cellular response allows for widespread bacterial proliferation, leading to the manifestation of these extensive lesions.

It is important to note that this contrasts with tuberculoid leprosy, where the immune response is more effective, resulting in fewer, well-defined lesions due to better containment of the bacteria. Thus, the correct characterization of the immune response in this context is that the individual demonstrates a selective inability to mount an adequate cellular response to Mycobacterium leprae.