• Significant decrease in total lymphocytes including CD4+ and CD8+ T cells was observed in ICU patients as compared to non-ICU. Both CD4+ and CD8+ T cells exhibited activated phenotype. However, no changes were observed in B cells and NK cells between ICU and non-ICU patients.• Higher percentage of inflammatory monocytes were detected in COVID-19 patients, with further increase in ICU patients. These monocytes were shown to secrete higher levels of GM-CSF and IL-6. Here, CD4 is linked to COVID-19.