Thread by @GertrudRey

Vaccines, convalescent plasma, and monoclonal antibodies.

What is the difference between these three things and what do they have in common? A thread. (1/n)

The major shared feature is that they all involve the action of antibodies, but the source of the antibodies and their durability is vastly different. (2/n)

Vaccines present or lead to the presentation of an antigen (e.g., a piece of a virus) that induces your immune system to make your own antibodies. Those antibodies stay in your body for a long time and are affiliated with an immune memory that lasts even longer. (3/n)

That means that even if your antibody levels are super low years later, your memory cells are able to reproduce those antibodies in huge quantities if they should see the same antigen again. (4/n)

Convalescent plasma is the blood plasma of a person who has recovered from an infection, and contains antibodies to the infectious agent (like a virus). (5/n)

When you receive convalescent plasma, the antibodies in the plasma should function the same way your own antibodies would and eventually get rid of the infectious agent. However, they are not your own antibodies and thus their durability in your body is limited. (6/n)

Eventually they degrade and there is no immune memory. This means that if you become infected again, you won’t have pre-existing antibodies or memory cells against that agent. (7/n)

Plasma also contains many other components, including clotting factors, which are problematic in the context of COVID-19 because they are associated with more severe disease and lead to an increased risk of death. (8/n)

The antibodies in convalescent plasma are “polyclonal”, meaning that they are derived from many different B cell lineages and may target many different portions of an antigen. (9/n)

Monoclonal antibodies (like bamlanivimab, or “bam bam”) are made in the lab, are derived from a single B cell lineage, and target a single epitope (or group of epitopes). (10/n)

The advantage of using monoclonal antibodies rather than convalescent plasma is that you don’t have all the other impurities that can be found in plasma (like clotting factors), and the action is more targeted and precise. (11/12)

Like with convalescent plasma, the durability of antibodies is limited and there is no immune memory.

Vaccination is also known as “active immunization,” while the administration of convalescent plasma and monoclonal antibodies is also known as “passive immunization.” (end)