Figure 4.

Induction of lymphoma-antigen-specific T cell tolerance in terminal HOX11 transgenic mice. DCs and T cells were isolated from nontransgenic mice (), healthy HOX11 transgenic mice (), and HOX11 transgenic mice with terminal lymphoma (––▵––). Age- and sex-matched C57BL/6 mice () were also included. Cell lysates were prepared from either B220⁺ sorted lymphoma cells or unsorted, total spleen/lymphoma cells. T cells were stimulated twice at 6-day intervals with autologous DCs pulsed with either lymphoma cell lysates or OVA protein, harvested, and assayed for anti-HOX11 lymphoma-antigen-specific cytolytic activity against DC targets pulsed with B cell lymphoma lysates (a) or DC targets pulsed with total spleen/lymphoma lysates (c). Anti-OVA-specific CTL activity was assessed against DC targets pulsed with OVA protein (---▵---) (a). Generation of nonspecific C57BL/6 (---●---), nontransgenic (---■---), or HOX11 transgenic (---▴---) CTLs was assessed against unpulsed DC targets (a and c). These findings were confirmed by using lymphoma cell lysates from five additional HOX11 mice with terminal lymphoma. (b) Immunogenicity of lymphoma cell lysates and the in vivo generation of anti-lymphoma-specific CTLs in elderly, healthy nontransgenic and transgenic mice. Five 14-month-old littermates were used; one nontransgenic mouse, three premalignant transgenic mice, and one HOX11 transgenic mice with terminal lymphoma. The four healthy littermates were injected with DCs pulsed with B220⁺ lymphoma cell lysate originating from the fifth littermate, they were given booster injections twice and then killed, and their spleens were used as a source of T cells. In vivo generation of lymphoma-specific cytolytic activity was assessed against B220⁺ lymphoma cell targets and LPS-activated C57BL/6 B cells.