In vitro targeting of erythrocytes to cytotoxic T‐cells by coupling of Thy‐1.2 monoclonal antibody

A method was explored to develop a general means to target erythrocytes to T‐cells in vitro. Mouse erythrocytes were coupled with an anti‐Thy‐1.2 monoclonal antibody by two methods. Chromic chloride coupling of antibody was preferred to biotinylation. The morphology, osmotic fragility, and the hematological values of treated cells were normal compared with those of control erythrocytes. Antibody‐coupled erythrocytes were incubated with cytotoxic T‐lymphocytes (CTLL) in vitro at a 20:1 ratio. Approximately 60–70% of the CTLL formed rosettes. The cell mixture was subjected to gradient centrifugation and separated into four fractions. THe rosettes were clearly identified only in the treated group containing anti‐Thy‐1.2‐coupled erythrocytes. No rosettes were found when aspecific monoclonal antibody was coupled to erythrocytes. Examination by scanning and transmission electron microscopy revealed CTLL with 4–5 erythrocytes attached to them but did not show any evidence of membrane fusion. Rosettes of CTLL incubated in vitro proliferated as well as CTLL alone and maintained their dependency on interleukin‐2. Targeting of erythrocyte carriers to lymphocytes offers the potential for delivery of molecules directly to the target cell.