Ultrastructural changes associated with response to challenge with anti-CD24 antibody. Left panel showing culture fixed at 3 h after challenged with isotype control antibody. (A) en face section showing close intercellular contacts are mediated by cell processes that are not uniformly distributed. (B) Cross-section showing close intercellular contact confined to the basal region abutting the polyester membrane (arrows). (C) Showing higher magnification of long junction (box in B) with close membrane association. Right panel showing similar preparation of a culture challenged with anti-CD24 antibody. (D) En face section showing more uniform intercellular contacts mediated by cell processes. (E) Cross-section showing extensive intercellular communication mediated by extensive cell processes (arrow indicates supporting polyester membrane). (F) Showing tight junction-like intercellular contact.