T helper cell polarization and the generation of varied antigen-dependent immune responses: a Markov chain model

Adaptive immune responses are deterministically classified into humoral or cell-mediated depending on the pattern of Th cell polarization into Th1 or Th2. Evidence suggests that the process of Th polarization is stochastic, however, the presence of some deterministic components has not been ruled out. Here, a Markov chain model that accounts for Th-mediated immune responses was developed based on the assumption that Th polarization and consequent transition events are stochastic.

Using assumed probability values, model analysis suggests that there is a rapid convergence to produce an immune response once the Th cell is stimulated by an antigen which is amplified as the number of transitions increases. The expected number of visits between Th and itself, B and itself and Tc and itself is about one whereas it is zero, less than one or degrees in the rest of the transition events depending on the interacting states.

Based on model analysis and validation, modeling Th-mediated immune responses as a Markov chain process seems to be plausible. The large degree of flexibility inherent in such a view of adaptive immunity can be helpful in addressing questions pertinent to Th function and behavior.