Inhibition of leukocyte candidacidal activity by serum from patients with disseminated candidiasis.

The effect of normal serum and serum for seven patients with disseminated candidiasis (DC) on candidacidal activity of normal human neutrophils (PMNL) was studied. PMNL incubated in DC serum had depressed candiacidal activity when compared to studies with normal serum. The candidacidal defect was not related to differences in particle uptake since phagocytic indices were similar with either normal or DC serum. DC serum did not affect PMNL bactericidal activity against Staphylococcus aureus. When Candida albicans (CA) was incubated in either normal or DC sera, washed, and added to PMNL in normal serum, pronounced inhibition of candidacidal activity was seen in all studies with CA previously incubated in DC serum. Dilution of DC serum or absorption of DC serum with heat-killed CA reversed the candidacidal defect. Ultrastructural studies of phagocytized CA demonstrated small ("tight") phagolysosomes and a delay in breakdown of an electron-dense coating on CA previously incubated in DC serum when compared to controls. Inhibition of leukocyte candidacidal activity appeared to be related to high titers of IgG antibodies against CA present in DC serum.