Human Immunodeficiency Virus (HIV) is a virus that infects (and destroys) Helper T Cells. As a result, people who are HIV+ generally have a low number of these T Cells. How would the dramatic decrease in Helper T Cells caused by HIV affect a person’s immune response? Be specific using details from what you learned about the immune response.

HIV invades various immune cells (e.g., CD4+ T cells and monocytes) resulting in a decline in CD4+ T cell numbers below the critical level, and loss of cell-mediated immunity − therefore, the body becomes progressively more susceptible to opportunistic infections and cancer.

HIV infects and deletes CD4+ T cells that normally coordinate the adaptive T- and B-cell response to defend against intracellular pathogens. The immune defect is immediate and profound: At the time of acute infection with an AIDS virus, typically more than half of the gut-associated CD4+ T cells are depleted, leaving a damaged immune system to contend with a life-long infection.

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?