1/ Immunology Comix - Summary: 1. Virus must get through mucous membranes, a physical barrier. 2. Innate immunity can destroy virus before it starts. 3. Neutralizing antibodies and memory B cells protect against future infection 4. T cells destroy infected cells

2/Immunology Comix - The first line of defense against respiratory viruses is the mucosal barrier in the nose/lungs. It is a physical defense, later amplified by adaptive mucosal immunity. The cilia, cells and various basement membranes prevent virus from entering the body.

3/ Immunology Comix - next up is innate immunity. Certain receptors on cells in this pathway can distinguish viruses, and produce inflammatory cytokines, which attract phagocytic cells and immune cells. This can eliminate many viruses. https://virology.ws/2009/06/03/innate-immune-defenses/

4/ Immunology Comix- Finally, adaptive immunity. First, B cells with specific antibodies are amplified by T helper cells to become plasma cell antibody factories. After the initial infection they can remain in the body for decades as memory B cells. https://www.virology.ws/2009/07/03/adaptive-immune-defenses/

5/ Immunology Comix - if the antibodies are neutralizing, they can attach to circulating viruses in future infections and eliminate them/prevent attachment. They also reduce circulating virus during infection, but can easily be overwhelmed by virus #s. https://www.virology.ws/2009/07/24/virus-neutralization-by-antibodies/

6/ Immunology Comix - the cytotoxic T cell response, amplified by T helper cells kills viral infected cells. This is really important, because a single virus can produce huge numbers of virus in an infected cell "factory." Cytotoxic T cells clear virus in an active infection.

7/ Immunology Comix - sometimes the immune response can recruit non-specific cytotoxic cells which cause more harm than the virus. Example, hepatitis A acute infection.

8/ Immunology Comix - and sometimes the cytokines from T cells and other recruited cells can cause huge multi-organ damage, as appears to be the case with COVID-19 severe disease.

9/ Immunology Comix - finally, in some respiratory viruses, the wrong kind of non-neutralizing antibody can actually cause/amplify cytokine storm. This antibody dependent enhancement happens, for example, in Dengue fever https://www.cdc.gov/dengue/training/cme/ccm/page57857.html

10/ Fatal ADE occurred in a vaccine to the respvir, RSV, in the early 1960's when old fashioned formalin-inactivated viruses were used. This is one reason that a COVID-19 vaccine must be carefully evaluated for safety in many people. https://www.frontiersin.org/articles/10.3389/fmicb.2018.02991/full

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