Efalizumab Down-regulates CD25 Expression on FOXP3+ Regulatory T Cells and Exacerbates the...
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response to a variety of cellular insults, including growth factor or nutrient withdrawal, organelle damage and mis- folded proteins. Autophagy is rapidly induced in T lympho- cytes following antigenic stimulation and blockade of autophagic signaling greatly reduces T cell clonal expansion, suggesting that autophagy is primarily involved in promoting T cell survival. In contrast, a recently identified negative feedback loop involving FADD and caspase-8, limits the level of autophagy in T cells. Failure to activate caspase-8 during T cell mitogenesis leads to hyperactive autophagy and cellular death through a programmed necrotic mechanism. These findings suggest that crosstalk between these cellular processes is essential for T cell activation and homeostasis. doi:10.1016/j.clim.2010.03.176 T.65. Role of Host and Tumor CD200 Expression in Control of Local and Distant (metastatic) Growth of Breast Cancer in Mice Reg Gorczynski 1 , Nuray Erin 2 , Kai Yu 1 , Ismat Khatri 1 . 1 University Health Network, Toronto, ON, Canada; 2 Akdeniz University, Antalya, Turkey Previously, we explored the regulation of expression of the novel molecule CD200 on EMT6 mouse breast cancer cells following tumor challenge in control or immunocompromised female recipients, observing that levels of CD200 expression on tumor cells isolated from the primary implantation site increased markedly during growth in immunocompetent mice, while persistent low levels of expression were observed in NOD-SCID.IL-2γr−/− mice. Similar low levels of tumor CD200 expression were seen in mice with generalized overexpression of a CD200 transgene (CD200tg mice). We nevertheless observed faster local tumor growth in both CD200tg and NOD.SCID mice, with decreased evidence for a host immune reaction in lymph nodes draining the tumor (DLN). We now report investigations into the importance of CD200 expression (by the host and/or tumor cells) in breast cancer growth using limiting dilution cloning of tumor cells from DLN (vs contralateral lymph nodes, CLN), evidence for CD200-mediated regulation of metastasis in this breast cancer model. Mammary fat pad injection of control EMT6 tumor cells in normal mice led to fewer (∼ 10-fold) DLN metastatic colonies than when tumor cells were implanted into CD200tg mice. In contrast, CD200tg–EMT6 tumor cells produced relatively equal numbers of metastatic colonies in both control and CD200tg mice. Neutralization of expressed CD200 by noncytotoxic F(ab′)2 anti-CD200mAbs decreased EMT6 tumor metastasis at the same time as increasing de- tection of cytotoxic antitumor immune cells in DLN. Inde- pendent studies confirmed that increased number of macroscopic lung metastases were also seen using 4THMpc breast cancer cells injected orthotopically into CD200tg (vs control) mice. doi:10.1016/j.clim.2010.03.177 T.66. Efalizumab Down-regulates CD25 Expression on FOXP3 + Regulatory T Cells and Exacerbates the Autoimmunity in Primary Sjogren's Syndrome Dat Tran 1 , Lolita Bebris 2 , Ethan Shevach 3 , Gabor Illei 2 . 1 University of Texas Medical School at Houston, Houston, TX; 2 NIDCR/NIH, Bethesda, MD; 3 NIAID/NIH, Bethesda, MD Rationale: FOXP3 + regulatory T cells (Tregs) are central to the prevention of autoimmunity. Tregs expressed high level of CD25 and require IL-2 signaling for their function. Since CD25 is up-regulated with activation and LFA-1 is required, we hypothesize that efalizumab treatment would result in down-regulation of CD25 on Tregs and potential exacerbation of autoimmunity. Methods: Subjects with Sjogren's syndrome were enrolled in a phase II clinical trial for weekly injection of efalizumab (1 mg/kg) up to 25 weeks. Peripheral bloods were analyzed for Tregs by flow cytometry. Clinical conditions were measured by objective improvement in salivary and lacrimal flows and minor salivary gland (MSG) inflammation. RESULTS: All three subjects had progressive down-regulation of CD11a and CD18 on Tregs (CD4 + FOXP3 + ), which correlated with dramatic decrease in CD25. The frequency and level of FOXP3 in the Tregs were not affected. There was no clinical improvement but instead repeat MSG biopsy showed signifi- cant increase in inflammation. Two subjects developed anti- dsDNA; one of whom developed multiple autoantibodies and lupus-like syndrome which resolved after efalizumab discon- tinuation. There was also significant increase in serum IgG. Conclusions: Efalizumab exacerbates Sjogren's syndrome and induces significant increase in local inflammation and systemic autoimmunity. Inhibition of LFA-1 interaction on Tregs negatively affected their CD25 without altering their FOXP3. These results suggest that Tregs are continually interacting with their target cells via LFA-1 and disruption of this interaction with efalizumab inhibits their activation, expres- sion of CD25, and suppressor function. This study cautions the potential detrimental effect of efalizumab on Tregs and autoimmunity. doi:10.1016/j.clim.2010.03.178 T.67. Do Dendritic Cells Participate in the Immune Response to T-independent Antigens Type 2? Dmitriy Khochenkov, Marina Gavrilova, Ekaterina Sidorova. Mechnikov Research Institute for Vaccines and Sera, Russian Academy of Medical Sciences, Moscow, Russian Federation Dendritic cells (DCs) belong to the most effective antigen- presenting cells. Their role in the presentation of thymus- depending antigens is well known. At the same time, the participation of DC in the immune response to T-independent antigens type 2 (TI-2 antigens) is almost not studied. The ability of DC to initiate the immune response to TI-2 antigens-α (1→3) dextran (Dex) and Streptococcus pneumoniae polysaccharide type 3 (SIII) is now investigated. Mouse bone marrow derived DC were generated by culturing of precursors with GM-CSF and then DCs were charged by TI-2 antigens. The pulse induced DCs S58 Abstracts
Transcript of Efalizumab Down-regulates CD25 Expression on FOXP3+ Regulatory T Cells and Exacerbates the...
S58 Abstracts
response to a variety of cellular insults, including growthfactor or nutrient withdrawal, organelle damage and mis-folded proteins. Autophagy is rapidly induced in T lympho-cytes following antigenic stimulation and blockade ofautophagic signaling greatly reduces T cell clonal expansion,suggesting that autophagy is primarily involved in promotingT cell survival. In contrast, a recently identified negativefeedback loop involving FADD and caspase-8, limits the levelof autophagy in T cells. Failure to activate caspase-8 during Tcell mitogenesis leads to hyperactive autophagy and cellulardeath through a programmed necrotic mechanism. Thesefindings suggest that crosstalk between these cellularprocesses is essential for T cell activation and homeostasis.
doi:10.1016/j.clim.2010.03.176
T.65. Role of Host and Tumor CD200 Expression inControl of Local and Distant (metastatic) Growth ofBreast Cancer in MiceReg Gorczynski1, Nuray Erin2, Kai Yu1, Ismat Khatri1.1University Health Network, Toronto, ON, Canada; 2AkdenizUniversity, Antalya, Turkey
Previously, we explored the regulation of expression ofthe novel molecule CD200 on EMT6 mouse breast cancer cellsfollowing tumor challenge in control or immunocompromisedfemale recipients, observing that levels of CD200 expressionon tumor cells isolated from the primary implantation siteincreased markedly during growth in immunocompetentmice, while persistent low levels of expression wereobserved in NOD-SCID.IL-2γr−/− mice. Similar low levels oftumor CD200 expression were seen in mice with generalizedoverexpression of a CD200 transgene (CD200tg mice). Wenevertheless observed faster local tumor growth in bothCD200tg and NOD.SCID mice, with decreased evidence for ahost immune reaction in lymph nodes draining the tumor(DLN). We now report investigations into the importance ofCD200 expression (by the host and/or tumor cells) in breastcancer growth using limiting dilution cloning of tumor cellsfrom DLN (vs contralateral lymph nodes, CLN), evidence forCD200-mediated regulation of metastasis in this breastcancer model. Mammary fat pad injection of control EMT6tumor cells in normal mice led to fewer (∼10-fold) DLNmetastatic colonies than when tumor cells were implantedinto CD200tg mice. In contrast, CD200tg–EMT6 tumor cellsproduced relatively equal numbers of metastatic colonies inboth control and CD200tg mice. Neutralization of expressedCD200 by noncytotoxic F(ab′)2 anti-CD200mAbs decreasedEMT6 tumor metastasis at the same time as increasing de-tection of cytotoxic antitumor immune cells in DLN. Inde-pendent studies confirmed that increased number ofmacroscopic lung metastases were also seen using 4THMpcbreast cancer cells injected orthotopically into CD200tg (vscontrol) mice.
doi:10.1016/j.clim.2010.03.177
T.66. Efalizumab Down-regulates CD25 Expressionon FOXP3+ Regulatory T Cells and Exacerbates theAutoimmunity in Primary Sjogren's SyndromeDat Tran1, Lolita Bebris2, Ethan Shevach3, Gabor Illei2.1University of Texas Medical School at Houston, Houston,TX; 2NIDCR/NIH, Bethesda, MD; 3NIAID/NIH, Bethesda, MD
Rationale: FOXP3+ regulatory T cells (Tregs) are central tothe prevention of autoimmunity. Tregs expressed high level ofCD25 and require IL-2 signaling for their function. Since CD25 isup-regulated with activation and LFA-1 is required, wehypothesize that efalizumab treatment would result indown-regulation of CD25 on Tregs and potential exacerbationof autoimmunity. Methods: Subjects with Sjogren's syndromewere enrolled in a phase II clinical trial for weekly injection ofefalizumab (1 mg/kg) up to 25 weeks. Peripheral bloods wereanalyzed for Tregs by flow cytometry. Clinical conditions weremeasured by objective improvement in salivary and lacrimalflows and minor salivary gland (MSG) inflammation. RESULTS:All three subjects had progressive down-regulation of CD11aand CD18 on Tregs (CD4+FOXP3+), which correlated withdramatic decrease in CD25. The frequency and level of FOXP3in the Tregs were not affected. There was no clinicalimprovement but instead repeat MSG biopsy showed signifi-cant increase in inflammation. Two subjects developed anti-dsDNA; one of whom developed multiple autoantibodies andlupus-like syndrome which resolved after efalizumab discon-tinuation. There was also significant increase in serum IgG.Conclusions: Efalizumab exacerbates Sjogren's syndrome andinduces significant increase in local inflammation and systemicautoimmunity. Inhibition of LFA-1 interaction on Tregsnegatively affected their CD25 without altering their FOXP3.These results suggest that Tregs are continually interactingwith their target cells via LFA-1 and disruption of thisinteraction with efalizumab inhibits their activation, expres-sion of CD25, and suppressor function. This study cautions thepotential detrimental effect of efalizumab on Tregs andautoimmunity.
doi:10.1016/j.clim.2010.03.178
T.67. Do Dendritic Cells Participate in the ImmuneResponse to T-independent Antigens Type 2?Dmitriy Khochenkov, Marina Gavrilova, EkaterinaSidorova. Mechnikov Research Institute for Vaccines andSera, Russian Academy of Medical Sciences, Moscow,Russian Federation
Dendritic cells (DCs) belong to the most effective antigen-presenting cells. Their role in the presentation of thymus-depending antigens is well known. At the same time, theparticipation of DC in the immune response to T-independentantigens type 2 (TI-2 antigens) is almost not studied. The abilityof DC to initiate the immune response to TI-2 antigens-α (1→3)dextran (Dex) and Streptococcus pneumoniae polysaccharidetype 3 (SIII) is now investigated. Mouse bonemarrow derived DCwere generated by culturing of precursorswithGM-CSF and thenDCs were charged by TI-2 antigens. The pulse induced DCs
