Tissue homeostasis and immunity: more on models

This was written in response to Colin Anderson's paper published in the same journal in April 2006.

The complete article is now available (free access) at the [Scand J Immunol].

In retrospect...

There is always something that I would like to change if possible and here the first would be this sentence in the abstract:

"They have often based their discussions around facts that have been established by experimental investigation"

"They have usually based their discussions around detailed experimental observations that are now paraded as facts."

Further on in the abstract I say:

"The perception of this function (of all or part of the immune system) is influenced by long established theories in immunology (e.g. horror autotoxicus, clonal deletion in utero, pathogen elimination, clonal selection, auto-immunity and so on) which, for many, have become enshrined as facts."

The intended message here would be clearer if the last four words were added.

In the first paragraph in the first column of page 175, these extensions to the descriptions at the end of the paragraph may make the process more understandable. The original sentence reads like this:

"Every epitope that reaches lymphocyte attention leads to an activation into either aggression (following catastrophic cell demise: a disruptive encounter) or tolerance (following controlled-cell shutdown: a non-disruptive encounter)."

Clearer understanding should follow by expanding this sentence to:

"Every epitope that reaches lymphocyte attention leads to an activation into either aggression (following catastrophic cell demise and the littering of the intercellular space with the debris of ruptured cells: a disruptive encounter) or tolerance (following controlled-cell shutdown and the rapid and safe disposal of the consequent membrane packaged debris: a non-disruptive encounter)."

And!!! I have carelessly allowed an "epitope" to appear where it should have been a "paratope" (epitope equivalent to antigen and paratope equivalent to antibody). This occurs in the second paragraph on page 174 where:

"RAG genes cannot, alone, explain how a diverse set of epitopes were suddenly created and simultaneously attached to a complex effector mechanism (all it shows is how the diversity of paratopes was rapidly expanded)."

Of course, it should read as below (I managed to get it right within the brackets so it seems strange that I got it wrong in the main sentence!).

"RAG genes cannot, alone, explain how a diverse set of paratopes were suddenly created and simultaneously attached to a complex effector mechanism (all it shows is how the diversity of paratopes was rapidly expanded)."

I have added a page with the results of a Google search done on the 25th September 2006 for the "purpose of the immune system". From this it is clear that there was very little doubt, on this date, that the system was seen as a bug hunting and killing mechanism.

In this article I have caricatured the "purpose" I have sensed in the various models of the function of the immune system. There are other models championed by authors that I have omitted to caricature here (notably Irun Cohen, Antonio Coutinho and other contributors in the June 2000 edition of Seminars in Immunology).

And, a final point: I have defined the derivation of the term pathogen as coming from the Greek for "birth of pain". I did find this definition somewhere but, it is more precisely defined as the "birth (or origin") of suffering (pathos). I now find this "birth of pain" definition embarrassing and wish I had not used it.

In the last paragraph of page 173, going over to page 174, I have talked about morphostasis, emergence and general systems theory. It highlights "how order can emerge out of apparently chaotic conditions by the accumulation of chance advantages that, with the help of a little free external energy, manage to amplify, catalyse and, eventually, sustain themselves." . . . . . "Systems theory can help to analyse living systems from the emergence of order in chemical–soups to complex social systems (the evolution of humans comes in between). The wider universe, itself, demonstrates many systems of emergent order (atomic systems, solar systems, galaxy systems)."

This theme is expanded extensively in the following article by Eric Chaisson: . There is more on "Big History" in Wikipedia .