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Measurement of Cytotoxic T Lymphocyte Diversity and Clonality in the Alloreponse of Acute Cellular Rejection Following Solid Organ Transplantation and the Early T Cell Immune Response in Human Immunodeficiency Virus-1 Infection

  • Author(s): Kim, Joseph Younghan
  • Advisor(s): Yang, Otto O
  • et al.
Abstract

Cytotoxic T cells (CTL) play a central role in providing protective immunity in humans by eliminating infected cells and establishing immunologic memory against re-infection. The study of modern immunobiology has made many significant discoveries into the mechanisms involved in the CTL response against foreign allogeneic cells (alloresponse) and infecting pathogens. Using technologies refined in our laboratory for the study of genetic diversity in T cell populations, we have investigated how to effectively implement therapies to control alloresponses that lead to immune mediated disease, as well as examined the factors that direct a more effective antiviral response.

The population of lymphocytes mediating acute cellular rejection after solid organ transplantation is restricted in the usage of specific genetic elements of the T cell receptor (TCR) gene. We have shown this genetic bias in the graft infiltrating lymphocyte (GIL) population mediating rejection persists throughout periods of undetectable to severe clinical rejection. In order to make use of this genetic restriction to implement more narrowly directed immunomodulatory therapies to treat acute rejection, we have developed an approach to categorize and predict these biases based on the alloreactive surface antigens present in donor and host. We have also devised a strategy to characterize CTL alloresponses within smaller populations of lymphocytes, allowing for the ability to detect and monitor for acute rejection through safer clinical sampling.

The immune response against HIV-1 infection is initially mediated by virus specific CTL, and this early response is likely key in determining the overall outcome of disease. We investigated how clonal breadth can influence the ability of the CTL response to avoid viral evasion in acute HIV-1 infection. We identified the HIV-1 specific CTL responses and target epitopes in six acutely infected individuals and tracked the evolution of viral variant species throughout early infection. CTL isolated ex vivo from these subjects demonstrated a limited ability to expand after activation in culture, constraining our ability to measure breadth based on cell expansion. We therefore developed a method to measure the clonal breadth of CTL responses based on cytokine secretion, allowing for breadth to be studied in acute infection without the limitations of poor ex vivo expansion of CTL. Our findings will give insight into the development of more effective cellular immunity based vaccines and gene therapies.

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