Kinetics of CD4 T Cell Cytokine Production, Chemokine Production and Activation after Influenza Vaccination

Abstract

Thesis (Ph.D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Microbiology and Immunology, 2012.The amount and timing of effector molecule secretion are tightly regulated in CD4 T cells during the immune response. T cell cytokine profiles have been studied extensively, but how chemokines are expressed during activation is less clear. This study showed that human CD4 T cells, activated with either influenza antigen or polyclonal stimulation, produce chemokines and cytokines with different kinetics. IL-2, IFNγ and TNFα were quickly induced, while chemokines CCL1, CCL3 and CCL4 were secreted later. Further analysis of sorted early cytokine positive cells showed that even though the IFNγ and IL-2 secreting cells have a preference to subsequently produce chemokines, the majority of chemokine producing cells did not secrete cytokines at early times. In addition to analyzing expression kinetics in individual cells, the kinetics of expansion of cytokine/chemokine-secreting cells during the human immune response to influenza vaccination were measured. The numbers of influenza-responsive CD4 T cells able to secrete chemokines increased transiently, 7 days after influenza vaccination, while the cytokine response did not change significantly. The response was then tracked more precisely by daily sampling, and monitoring of the proliferation marker Ki-67. These two improvements revealed that a substantial fraction of influenza-specific CD4 T cells responded to vaccination. After 4-6 days, there was a sharp rise in the numbers of Ki-67- expressing cells that produced cytokines or chemokines in vitro in response to influenza vaccine or peptide. Ki-67+ cell numbers then declined rapidly, and ten days after vaccination, both Ki-67+ and overall influenza-specific cell numbers were similar to pre-vaccination levels. The response to Live Attenuated Influenza Vaccine was similar, but had slightly slower kinetics and higher peak responding cell numbers. Overall, these results demonstrate that CD4 T cells secrete cytokines and chemokines with different kinetics. Ki-67 and chemokine expression are sensitive tools for assessing the quality and quantity of responses to different influenza vaccines, and reveal a response to inactivated influenza vaccine that was difficult to detect by previous methods. These results also raise the possibility that vaccination may substantially reshape the anti-influenza T cell memory response, even without significant changes in the overall memory cell numbers