CD28 and chickenpox: The lymphocyte proliferation test at onset showed a strong reduction of the TCR-mediated response to anti-CD3 and anti-CD3/anti-CD28 and IL-2 compared with healthy controls, while the response to polyclonal stimuli (PHA, pokeweed mitogen [PWM]) and to tetanus, varicella and alloantigens were present, although the antigen-specific response is poor, in line with the lack of memory T cells (particularly CD8+) (Fig. 1 B).