A monoclonal antibody exhibiting reactivity with both X‐hapten‐ and lactose‐bearing glycolipids

Abstract: The tissue reactivity of a monoclonal antibody raised against human granulocytes, FMC 34, was shown to overlap with antibodies including FMC 10, which is directed against the X‐hapten, and with T₅A₇, which is directed against lactose‐bearing antigens. Reactivity of FMC 34 on sections of human cornea was more widespread than that of either FMC 10 or T₅A₇. High sensitivity fluorescence testing revealed that both FMC 34 and T₅A₇ reacted weakly with the T‐lymphocyte cell line JM, unlike the CD 15 antibody FMC 10. Competitive binding experiments showed that binding of FMC 34 to granulocytes was inhibited by preincubation with T₅A₇, while FMC 34 itself was able to inhibit the binding of both FMC 10 and T₅A₇. The binding of FMC 10 was not inhibited by preincubation of cells with T₅A₇. Saturation‐binding analyses revealed that each human granulocyte could bind 17.5 × 10⁵ molecyles of FMC 34, which was more than three times the number of molecules of FMC 10 which could be bound to each cell. The additional reactivity of FMC 34 appears to be due to its capacity to bind fucosylated and non‐fucosylated lactose‐bearing structures.