Lymphocyte and mastocytoma (P815) cell populations incubated with DNP-phosphatidylethanolamine in the form of liposomes displayed cell surface hapten as evidenced by: i) 125I-anti-DNP antibody binding; ii) C-mediated lysis, and iii) K-cell mediated lysis. Under optimal conditions, P815 cells incubated with DNP-liposomes showed a higher DNP density than was obtained by direct surface haptenation with dinitrobenzene sulfonic acid (DNBS). Moreover, the DNP transferred via cell-liposome interactions persisted on the cell surface at least as long as that introduced by DNBS.

Despite ready accessibility to antibody, the cell surface hapten introduced by cell-liposome interaction was not recognized by hapten-specific cytotoxic T cells. Thus, cells bearing liposome-derived DNP- (or TNP-) could not serve as targets for H-2 restricted hapten-specific effector cells; did not competitively inhibit the lysis of DNBS- (or TNBS-) modified cells; and, furthermore, did not stimulate hapten-specific cytotoxic cells in either primary or secondary responses. Interestingly, membrane preparations obtained from TNBS-treated cells did not “trigger” primary or secondary hapten-specific cytotoxic responses, although the same preparations readily stimulated “primed” allogeneic cells.

In contrast to the results obtained with cells bearing lipid-associated hapten, the addition of haptenated (DNP- or TNP-) bovine serum albumin (BSA) to lymphocyte cultures readily stimulated H-2 restricted, hapten-specific, cytotoxic T cell production. Cells incubated with DNP- (or TNP-) BSA for even brief (60 to 90 min) periods became susceptible to attack by syngeneic hapten-specific effector cells and specifically inhibited the lysis of syngeneic cells modified with the appropriate nitrobenzene sulfonic acid.


This work was supported by Grant AI 15383 (formerly AI 10280) from the National Institutes of Health.

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