Question

The scenario: an arthropod vector takes a blood meal from a human host and introduces a bacterial pathogen. This particular pathogen is initially an intracellular pathogen, travels to secondary lymph tissue where it returns to being extracellular and quickly replicates. To complete this assignment I want you to tell the story of this pathogen’s life journey from the pathogen’s perspective and then tell that same story from the perspective of the immune system. Be sure to include the sequence of events, molecular mechanisms used to achieve specific goals and remember you aren’t a successful pathogen unless you make it into another host. Give as much detail as possible.

Answer 1

The parasite story:
1: The arthropod vector sucks the blood and inoculate the pathogen into the blood.
2: The pathogen reaches the liver cells or any other target cells through blood.
3: It multiplies in the cells and then invades the bloodstream.
4: The veins that connect the blood circulation with lymphatic vessels carry it to the lymphatic vessels.
5: It reaches the secondary lymphoid tissue (lymphatic nodes) via lymphatic vessels.
6: It escapes the lymphatic nodes and enter the blood stream again to replicate.
7: When other arthropod bites the infected person for meal, it carries the pathogen along with blood to the some other healthy person.
Immune system:
1: Innate immune responses are first line of defense of body.
2: Skin serves as barrier for entry of pathogen into the blood. Bite of vectors causes inflammation reaction which is also non specific defense of the body.
3: Inflammation process includes redness, production of heat and swelling in the region of bite.
4: There is increased permeability of capillaries in inflammed region to allow the macrophages and neutrophils to squeeze out of the capillaries.
5: These phagocytic immune cells serve to kill the pathogen.
6: The pathogen escapes and enter the liver cells and then the lymph nodes.
7: The B cells encounter the pathogen and are activated to carry out clonal propagation.
8: The division in B cells forms the plasma cell which in turn produce antibodies against the pathogen.
9: The antibodies have antigen binding site which recognize and bonds to the specific protein/component present on the surface of pathogen.
10: Antibodies try to kill the pathogen but the pathogen has increased its number. Presence of RNA genome allows it to mutate rapidly and to change its antigen rapidly.
11: Changes in antigen allows the pathogen to escape from the antibodies in lymphnodes and blood stream.