An iglA mutant lacks the expression of a 21 kDa protein. Western blot showing the lack of an anti-IglA serum reactive 21 kDa protein in the ΔiglA strain (top panel). Wild type levels of IglC are retained in the ΔiglA strain (bottom panel). In contrast, the iglA::Em mutant lacks expression of IglC. The expression of IglC is threefold lower in an iglB::Em strain than in JLO and ΔiglA. Fluorescence intensity was used to quantify relative amounts of protein.