Travel to Health

  Line of Defense Timeline Cells Antigen Dependency Examples Innate (non-specific) First Immediate response (0 -96 hours) Natural killer cells, macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils Independent Skin, hair, cough, mucous membranes, phagocytes, granulocytes Adaptive (specific) Second Long term (>96 hours) T and B lymphocytes Dependent Pus, swelling, redness, pain, T and B lymphocyte response Table 1.  Innate immune response vs adaptive immune response (source: [3]) Figure 1.  DCs—Messengers between Innate and Adaptive Immune Systems Dendritic cells (DCs) represent a heterogeneous family of immune cells that link innate and adaptive immunity . The main function of these innate cells is to capture, process, and present antigens to adaptive immune cells and mediate their polarization into effector cells . Figure 2.   COVID-19 vaccines immune activation modes (Source: [8]) Dendrite Cells Dendritic cells  (DC) are...

Any virus that can cause disease in humans must have at least one immune evasion mechanism—at least one immune evasion “trick.” Without the ability to evade the immune system , a virus is usually harmless .  In the case of SARS-CoV-2, the virus is clearly unusually effective at evading the triggering of early innate immune responses , such as type 1 interferons (IFNs) (see below). It is plausible that much of the nature of COVID-19 as an illness is a consequence of this one big trick of SARS-CoV-2 . Transient lymphopenia is a common feature of many respiratory viral infections, such as with influenza A H3N2 virus, human rhinovirus or respiratory syncytial virus, but lymphopenia in these other infections typically occurs for only 2–4 days around symptom onset and rapidly recovers. By contrast, COVID-19-associated lymphopenia may be more severe or persistent than in these other infections and seems to be more selective for T cell lineages . [20] Thus, although the mechanisms of l...