Optiоnаl up tо 2 pоints of extrа credit: A recent study out of Chinа (Jiang et al. 2025. "Persistent Attenuation of Lymphocyte Subsets After Mass SARS-CoV-2 Infection") used flow cytometry to measure lymphocytes in patients undergoing lymphocyte subset testing at three hospitals during three time periods of the pandemic that they defined: pre-COVID, the period of mass infection when China dropped COVID controls, and post-COVID infection. They found that during the period of mass infection, T cells, CD4+ helper T cells, CD8+ cytotoxic T cells, Natural Killer (NK) cells, and B cells in their samples dropped significantly relative to their pre-COVID samples. Even at 20 months post-infection, cytotoxic T cells remained at somewhat reduced levels, variable by sex, age, and health status. For each of these - helper T cells, cytotoxic T cells, NK cells, and B cells - what would the impact on the patient be of a reduced population of cells during and following infection by SARS-CoV-2? Please number your parts 1 through 4 and briefly identify the role of each type of cell and the likely impact of a reduced population of such.