The immune system attacks pathogens in a series of programmed activities. Mast cells (a/k/a mastocyte or labrocyte) are the first immune cells to reach pathogens. Leukocytes (white blood cells, i.e. neutrophils, monocytes, macrophages, eosinophils, basophils); and lymphocytes (T-cells, B-cells, natural killer cells), attack the pathogen, and transport the pathogen to the plasma cells. The plasma cells (a/k/a plasma B-cells, plasmocytes, or effector B-cells), are transported by the lymphatic system, and make and secrete large quantities of antibodies to specific pathogens.
Different types of immune cells attack different types of pathogens. For instance, mast cells and macrophages attack chlamydia pneumonia; neutrophils attack H-pylori and psittacosis; and monocytes attack parasites. When the immune system cannot eradicate pathogens, the immune cells generate molecules that signal a higher level of inflammation.
Molecules generated by immune cells to signal a need for a higher level of inflammation are unique to each type of immune cell, and collectively referred to as cytokines. Cytokines include lymphokines, monokines, interferons, chemokines, TNF-alpha, etc. Immune cells can also become infected in the attack, which weakens the immune response and can cause excessive inflammatory signals from immune cells.
The type of cytokines generated in covid-19 patients is a clue to the type of immune cells generating the cytokines, which may be a clue to the unique underlying co-infections in severely ill covid-19 patients. Co-infections may explain differing modes of attack and variations in disease severity; why some patients suffer cytokine storms; and the unique needs of severely ill covid-19 patients.
https://www.nytimes.com/2020/08/04/health/coronavirus-immune-system.html
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