Got COVID and Did Not Feel Sick? Here’s Why. Researchers from the University of California San Francisco (UCSF) have revealed a potential HLA gene (HLA B15:01) that helps create polyfunctional cross reactive CD8+ T cells with memory function. These T cells are produced when people with these genes are exposed to human coronavirus. However, these T cells are capable of attacking a conserved/similar region of SARS-COV-2 leading to asymptomatic disease.