Major histocompatibility complex class I (MHCI) and MHCII proteins differ in structure and sequence. To understand how T cell receptors (TCRs) can use the same set of variable regions to bind both proteins, we have presented the first comparison of a single TCR bound to both MHCI and MHCII ligands. The TCR adopts similar orientations on both ligands with TCR amino acids thought to be evolutionarily conserved for MHC interaction occupying similar positions on the MHCI and MHCII helices. However, the TCR antigen-binding loops use different conformations when interacting with each ligand. Most importantly, we observed alternate TCR core conformations. When bound to MHCI, but not MHCII, Vα disengages from the Jα β-strand, switching Vα’s position relative to Vβ. In several other structures either Vα or Vβ undergoes this same modification. Thus, both TCR V-domains can switch among alternate conformations, perhaps extending their ability to react with different MHC-peptide ligands.

Introduction: Asian Americans make up a sizable minority in the US, with Chinese currently making up the largest subgroup. However, despite this fact, the majority of Chinese women in North America underutilize Pap testing and carry a disproportionately higher rate of invasive cervical cancer. It has been suggested that certain cultural beliefs and practices can interfere with Western health care utilization among newly arrived immigrant communities. Methods: Fifteen hundred thirty-two women ages 20 to 69 from Seattle, Washington and Vancouver, BC were interviewed in person in 1999, and data from 993 participants were analyzed. Results: Women who observed postpartum rituals or who believed that certain aspects of their rituals help prevent them from obtaining cervical cancer did not show an underutilization of Pap testing. However, other factors, such as having a car in the household, speaking English, or being married, were highly predictive of Chinese women's Pap test utilizations. Discussion: Based on these findings, postpartum practices do not seem to negatively influence Pap test utilization among Chinese women in North America. Instead, clinicians serving Chinese in North America should focus more on economic, language, and acculturation as potential barriers for their patients' health care utilization.

We tested the effects of Rituximab (anti-CD20) and IDEC-152 (anti-CD23) on apoptosis of B-cell malignancies, using established non-Hodgkin’s B-Cell lymphoma cell lines and freshly isolated Chronic Lymphocytic Leukemia (CLL) B-cells. We used monolayers of stably transfected CHO-cells expressing FcRγIII-A to present antibody to B-cells and promote crosslinking. Established B-cell lymphomas (n = 3) were cultured in the presence of FcRγIIIA-expressing CHO monolayer with or without MAbs and apoptosis was measured by annexin V/propidium iodide staining at various times thereafter. Both antibodies induced time-dependent apoptosis of B-cell lymphoma cell lines. After 48 hrs of treatment with either Rituximab or IDEC-152, the majority of the malignant B-cells were apoptotic (remaining viable cells = 28.7% ± 0.2137% for Rituximab and 30.87% ± 0.7332% for IDEC-152). Rituximab and IDEC-152 also induced marked increases in caspase activity in B-cell lymphoma cell lines, with fold-increases above baseline control cells of 25 ± 0.9031 and 24 ± 0.3839, respectively. In contrast, neither Rituximab nor IDEC-152 induced striking effects on primary CLL B-cells (n = 6). We therefore tested the combination of Rituximab or IDEC-152 with other agents that target anti-apoptotic proteins, exploring whether more efficient induction of apoptosis can be achieved. We cultured lymphoma cell lines and primary CLL specimens with chemical antagonists of XIAP (Schimmer, et al. Cancer Cell5: 25, 2004), an anti-apoptotic protein that inhibits effector caspases. When used at concentrations where XIAP antagonists alone were non-apoptotic (approximately 2.5 μM), a significant increase in apoptosis was achieved in cultures of lymphoma and CLL cells treated with either Rituximab or IDEC-152. These findings suggest that Rituximab or IDEC-152 may more efficiently induce apoptosis of malignant B-cells when combined with an apoptosis-sensitizing agent. (Supported by CA-81534; CA-78040; and an unrestricted grant from Genentech, Inc.).

BackgroundImmunotherapy offers many potential advantages to traditional chemotherapy, including high specificity and low toxicity. One of the goals of immunotherapy is to generate tumor-specific cytotoxic lymphocytes (CTLs), which have the potential to specifically kill tumors. Tumor antigens have been used to elicit CTL responses. One disadvantage of using tumor antigens is that the CTLs that recognize these antigens are often of low affinity and/or low frequency. T cell epitopes can be engineered to enhance the expansion of tumor-specific CTLs. The challenge has been to identify such altered peptide ligands (APLs).Study Design and MethodsWe use a positional scanning synthetic combinatorial peptide library (PS-SCL) to identify superagonist peptides of NY-ESO-1, a tumor-associated antigen expressed in melanoma, ovarian cancer, and other solid tumors. This exhaustive search method looks at all amino acid combinations of 9mer peptides (approx. 209 peptides) in a positional scanning format. T cell killing of antigen-presenting cells loaded with the library was determined by chromium release assay. Biometric analysis of the data was used to identify candidate peptide sequences. These specific peptides were then tested and compared to the parental peptide NY-ESO-1 for enhanced target sensitization to lysis and capacity to elicit CTL responses in vitro.ResultsFour well-characterized high affinity NY-ESO-1-specific CTL clones were used to probe the combinatorial peptide library. Potential superagonist peptides for NY-ESO-1 were identified, ranked using a scoring algorithm, and then individually tested. We identified a novel core consensus sequence within the parental epitope that yielded enhanced CTL activity.ConclusionThrough these methods we have identified several novel superagonist ligands for T cell-based immunotherapy using NY-ESO-1-specific clones. Such peptides may show promise for both adoptive therapy and cancer vaccines.