LCK and infection: In order to analyse the effect of pneumococcal H2O2 on Lck activity in H441 cells infected with SpnWT, SpnΔply and SpnΔlctOΔspxB, Lck and p-Lck levels were measured using anti-Lck antibody and anti-phospho Tyr505-Lck antibody to detect alterations in the phosphorylation of Lck during infection.