In the context of COVID-19, why is it possible to inject someone else’s antibody protein into a person without fear of stimulating an immune response. Does this indicate that, somehow, antibody conformation is universal?

Or rather ...

The immune system must differentiate between cellular and fragmentary material? It will attack any cellular material it deems ‘non-self’. But if foreign non-cellular material enters the body, such as dust, pollen etcetera we are in the realm of an allergic response. The allergic response is not absolute: only certain materials will cause a reaction.

So perhaps foreign protein, such as donor plasma products, are treated as potential allergens which, happily, do not cause an immune response; unlike midge spittle?

  • $\begingroup$ Educating I find that you differentiate "between cellular and fragmentary material", this brings up "MHC". People differ in their allergic reactions as they differ in their MHC? If any sole protein, is "no cell", it might still be about the MHC, of the "host". Not commonly known is that antibody producing B cells take up isolated antigen without prior presentation by APCs. B cells then present on their MHC2 to T helper cells that need presentation by APC. Thesis: people differ in reaction because they differ in their MHCs presenting allergenes to TH1, 2 and their B cell's MHC2. $\endgroup$ Oct 29, 2021 at 12:38
  • $\begingroup$ Interesting: Likewise it might be asked if T cell receptors are interchangeable between individuals - as antibody is another word for the B cell receptor turned loose from the B cells membrane. Any T cell receptor isolated from one individuum and injected as "foreign" protein should be tolerated - it might even be taken from the horses' mouth as Behrings magic bullets were. $\endgroup$ Oct 29, 2021 at 12:42

2 Answers 2


The complexity of the immune response requires foreign proteins to be bound first by presenting cells which happen to be like macrophages - cells that are like garbage disposals. Why some proteins are simply gobbled up and yet others are preserved and presented to the resident T cell helper population is related to the size and sequence of the protein. In other cases, even small molecules (allergens) can bind to native normal proteins and make them look abnormal.

The use of immunoglobulin (semi purified blood) was used in treating certain diseases in the past. These sera were usually developed from animals purposely infected with the disease. Though these proteins also elicited their own immune response (side effects) the kinetics of that event was days to weeks whereas the binding of the immunoglobulin to its target(the virus protein) is a first order event occurring in minutes. Clearance of that antibody antigen complex over hours to days Avoids the catastrophic exponential growth of the virus by keeping the numbers low. Eventually tho side effects WILL happen if you keep giving the serum


Activation of the immune response relies on the detection of structure features of the foreign molecule that marks it as distinct from host cells. In the case of immunoglobulin injection between a human donor and a human recipient, these immunoglobulins are naturally produced antibodies that the body makes to help you fight infections and to serve other functions for the immune system. Therefore, they do not have the structural features that can be recognized and mark them as “foreign molecules” by the immune system.

However, IVIG can cause some adverse effects such as headache, chills, etc. You can find more details in this paper.


  1. Chaplin D. D. (2010). Overview of the immune response. The Journal of allergy and clinical immunology, 125(2 Suppl 2), S3–S23. https://doi.org/10.1016/j.jaci.2009.12.980
  2. https://www.rheumaderm-society.org/ivig/
  3. Guo Y, Tian X, Wang X, Xiao Z. Adverse Effects of Immunoglobulin Therapy. Front Immunol. 2018;9:1299. Published 2018 Jun 8. doi:10.3389/fimmu.2018.01299

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