ACUTE CYTOTOXIC ALLOGENEIC HISTOINCOMPATIBILITY REACTIONS INVOLVING GRAY CELLS IN THE MARINE SPONGE, CALLYSPONGIA-DIFFUSA

A variety of procedures were used in a study of the histoincompatibili ty reactions of Callyspongia diffusa. Rejection reactions as tradition ally tested between laterally apposed intact fingers cut from two diff erent sponges require about a week of contact to exhibit cytotoxicity. In a miniaturized assay involving reactions between small pieces of t issue snipped from sponges with scissors and pushed together on an ins ect pin, cytotoxicity is evident within 48 hours of contact. Reactions of cells dissociated by divalent cation removal and allowed to reaggr egate in seawater were also studied. Aggregates produced from allogene ic mixtures of cells from two individuals were killed by internal cyto toxic reactions within 36 hours of the initiation of aggregation. Afte r only one hour of aggregation, aggregates from allogeneic mixtures we re significantly smaller than aggregates of cells from a single indivi dual. This rapid slowing of aggregation is the earliest response to al logeneic contact that we noted and does not appear to reflect early cy totoxic processes, Apposition of an aggregate containing cells from on e sponge to an aggregate containing cells from a second individual lea ds to mutual destruction. Aggregates harvested and apposed 4 hours aft er initiation of aggregation begin to show mutual cytotoxicity at 36 h ours of contact. Aggregates placed in contact 48 hours after the initi ation of aggregation exhibit cytotoxicity within 8 hours. These rapidl y reacting 48-hour aggregates exhibit a pronounced accumulation of gra y cells at the boundary of allogeneic contact by 8 hours. These result s are interpreted as indicating at least five steps in the histoincomp atibility reactions of C. diffusa: (1) recognition soon after allogene ic contact; (2) generation of signals that suppress cell aggregation a nd cell movement and attract gray cells to the boundary of contact; (3 ) acceleration of the sponge immune response-including the responsiven ess of gray cells to accumulate at the boundary of allogeneic contact- by tissue trauma produced when the tissue is cut or dissociated it int o individual cells; (4) arrival of gray cells at the boundary of allog eneic contact; and (5) initiation of cytotoxic processes.