HAVCR1 and COVID-19: Additionally, sTIM-1 (soluble T-cell immunoglobulin and mucin protein-1), the soluble form of the co-stimulatory T cell receptor TIM-1 (TIM-1) known to be a key regulator of Th2 responses, showed at least 3-fold increase in moderate and severe COVID-19 cases (Figure 1F).