Dissecting causes of variation in immune defenses: the mysterious case of the swarming T-helper cells
Abstract: Individual-level heterogeneity drives ecological and evolutionary dynamics. The effects of individual variation are abundantly clear in host-parasite interactions: hosts exhibit remarkable heterogeneity in the strength, speed and specificity of their immune responses, which in turn generates varied susceptibility to infectious and autoimmune diseases and varied propensity to transmit disease. Why do hosts vary so much? One important explanation for host variation arises when T-helper cells polarize into worm-clearing and germ-clearing factions. Subtle differences in initial conditions can be amplified by the collective behavior of T-helper cells to generate radically different system-level responses in different hosts. I will outline how adaptive systems analysis is shedding light on the function of “agile swarms” of these cells during infection, including worm-germ co-infections.