An Enormous Number of Antigens

I’ve recently been reading through ‘The Green Book’ again. Delving a little deeper than usual and reading some of the references too.

Do Multiple Vaccines Overwhelm or Weaken the Infant’s Immune System?

Offit et al determine the diversity of the immune response by estimating the number of vaccines a child could respond to at one time.

They make 5 assumptions;

1. 10 ng/mL of antibody is an effective concentration of antibody per epitope. An epitope is part of a macromolecule that is recognised by an antigen.

2. generation of 10 ng/mL of antibody needs approximately 10^3 B cells/mL. B cells recognise antigens, are stimulated to proliferate and produce large numbers of lymphocytes secreting an antibody to the antigen.

3. a single B cell clone takes one week to reach 10^3 in number.

4. each vaccine contains about 100 antigens and 10 epitopes per antigen (10^3 epitopes).

5. approximately 10^7 B cells are present per mL of circulating blood.

If you are still with me this means that each child has, theoretically, the capacity to respond to about 10,000 vaccines at any one time.

(10^7 B cells per mL divided by  10^3 epitopes per vaccine)

This is likely a conservative estimate as many vaccines contain fewer than 100 antigens. For example, the Diphtheria and Tetanus vaccines each contain one antigen.

Looking at the first 12 months of the schedule for the UK’s routine childhood immunisations, there are 8 injections comprising about 20 vaccines.

Even if these 20 vaccines were all given at the same time, they only “use up” 20/10000 = 0.2% of the capacity of the immune response.

B cells and T cells are also constantly being replenished increasing the ability of the immune response further.

Pet Hate

Offit et al make the 5 assumptions by referring to this paper. My Athens account does not cover this publication. I would love to look at it but I’m not paying over 30 US dollars for the “privilege” of 24-hour access. The inaccessibility of research (the reference is from 1990!) is a pet hate of mine.

Take-home message

Infants have the capacity to respond to an enormous number of antigens.