CXCR4 and COVID-19: Given that both CCR6 and CXCR4 are involved in B cell circulation to lymph nodes, whereas CXCR3 (whose gene is located on X chromosome)1 rules B cell attraction to inflammation sites (Kunkel and Butcher, 2003), it would be worth deepening if BAL B cells from COVID-19 exhibit different B cell trafficking features according to both severity and gender.