Mathematical Models of Maintenance of Immunological Memory
Vitaly Ganusov (Department of Biology, Emory University)
(June 18, 2004 11:00 AM - 12:00 PM)
Immunological memory - the ability to "remember" previously encountered pathogens and respond faster upon re-exposure is a central feature of the immune response of vertebrates. We use models to consider the role of different factors such as exposure to pathogens, cross-reactive and bystander stimulation and homeostasis on the longevity of memory in the CD8 T cell population. We show that the longevity of memory, defined as the decline in the population of memory cell lineages is governed by the following rules:
- The average loss of cells in memory lineages is proportional to the number of cells of new (memory) specities generated following stimulation by new pathogens and inversely proportional to the size of the memory compartment.
- Cross reactive stimulation (i) reduces the average rate of loss of memory by reducing the magnitude of expansion of new naive lineages; (ii) the variation in the rate of decline in the populations of cells to different lineages is greatest at intermediate levels of cross-reactivity.
- The loss of memory is independent of bystander stimulation and the precise mechanism for the maintenance of homeostasis.