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Classification

Structural homology has been able to partially distinguish between cytokines that do not demonstrate a considerable degree of redundancy so that they can be classified into four types:

The four α-helix bundle family - Member cytokines have three-dimensional structures with four bundles of α-helices. This family in turn is divided into three sub-families:
1. the IL-2 subfamily
2. the intterferon (INF) subfamily
3. the IL-10 subfamily
The first of these three subfamilies is the largest. It contains several non-immunological cytokines including erythropoietin (EPO) and thrombopoietin (THPO). Alternatively, four α-helix bundle cytokines can be grouped into long chain and short chain cytokines.
the IL-1 family - It primarily includes IL-1 and IL-18.
the IL-17 family - It has yet to be completely characterised, though member cytokines have a specific effect in promoting proliferation of T-cells that cause cytotoxic effects.
Chemokines

A more clinically and experimentally useful classification divides immunological cytokines into those that promote the proliferation and functioning of helper T-cells, type 1 (IL-1, INF-γ etc.) and type 2 (IL-4, IL-10, IL-13, TGF-β etc.), respectively. A key focus of interest has been that cytokines in one of these two sub-sets tend to inhibit the effects of those in the other. This tendency is under intensive study for its possible role in the pathogenesis of autoimmune disorders.

Index