Uptake of antibody directed cytotoxic liposomes by CD3 on human T cells.

Using polyclonal human T cells and anti-CD3 monoclonal antibodies we have shown that small unilamellar liposomes covalently coupled with protein A become bound to T cells and not to B cells and that the binding was a specific liposome-antibody-receptor interaction. Intracellular delivery of liposome contents was demonstrated by the use of encapsulated carboxyfluorescein and flow cytometry and the transfer of membrane-bound liposomal carboxyfluorescein was virtually complete in 30 min. Liposomes containing methotrexate inhibited the growth of PHA-stimulated peripheral blood lymphocytes by 90%, after 48 h incubation. Potential applications are proposed in the study of the behaviour of surface membrane components and in T cell depletion and purging of bone marrow.