Question

Leishmaniasis is a disease that can either be fatal to its host or will be cleared by the immune response of the host. Which immune response is responsible for clearing the protozoan parasite that causes leishmaniasis?

A. TH17 cells

B. TH2 cells

C. complement

Answer 1

The answer is a T_H1 immune response that leads to the production of IFN .
But that won't probably make you understand much so let me explain it in a more detailed fashion.
The disease Leishmaniasis is caused by the parasite Leishmania major and this parasite lives in the phagosome of macrophages. So what the body does is to invoke a cellular response against this parasite so as to neutralize them. The body tries to invoke a T_H1 response and what is it ?. It stands for T helper cells which can only activate if the antigen is presented with class II MHC complex and this T cell expresses CD 4 + glycoprotein in their membrane. (A CD 8 + expressing T cell is known as T_C cell and it can be activated by MHC class I).
So how this T_H cell help in neutralizing the parasite?. It creates IFN or interferon-gamma that is crucial in having resistance against this parasite. A T_H2 response if happens does not help the host in any way and that leads to a fatal condition. So it must be stressed that certain immunological responses are crucial for having resistance against this pathogen, and if by chance the host has a mutation in the IFN receptor then that host is susceptible to Leishmania-induced fatality.

By the way, if you don't know about IFN it is a cytokine molecule that is released by T_H 1 cells and it has an inflammatory response as well as activating macrophages which in turn exhibit more expression of class II MHC molecules, increased cytokine production, and increased microbicidal activity.

For any query feel free to refer to the comment section & I will get back to you.