CD4 and long COVID-19: The proportion of IL-2 producing CD4+ T cells was significantly higher in RC participants compared to PASC participants in response to S, N and M proteins (P = 0.006, P = 0.003 and P = 0.005, respectively), while the proportion of TNF-α- and IL-2-producing N-specific CD4+ T cells was higher in pulmonary PASC participants (P = 0.0036).