At low precursor frequencies, the T-cell response to chronic self-antigen results in anergy without deletion

Long-term outcomes of stent-related perforation in malignant colon obstruction: a systematic review and meta-analysis

PURPOSE

The placement of self-expandable metallic stents as a bridge to surgery in malignant colon obstruction is concerning due to the long-term oncological results reported in recent published studies. The aim of this study was to evaluate the oncological consequences of stent-related perforations in patients with malignant colon obstruction and potentially curable disease.

METHODS

MEDLINE, Cochrane Library, Ovid and ISRCTN Registry were searched, with no restrictions. We performed five meta-analyses to estimate the pooled effect sizes by using a random-effect model. The outcomes were global, locoregional and systemic recurrence rate and 3 and 5 year-survival rate depending on the presence or absence of stent-related perforation.

RESULTS

Thirteen studies (950 patients) were included. The overall rate of stent-related perforation was 8.9%. The global recurrence rate was significantly higher in stent-related perforation group (41.2 vs. 30.8%; OR 1.70; 95%CI: 1.02-2.84; p = 0.04). Locoregional recurrence rate was higher in the perforated group than in the non-perforated group (26.6 vs. 12.5%), with statistically significant differences (OR 2.41; 95% CI:1.33-4.34; p = 0.004). No significant differences were found in systemic recurrence rate (13.6 vs. 20.5%; OR 0.77; 95%CI: 0.35-1.7; p = 0.51); 3-year overall survival rate (65.4 vs. 74.8%; OR 0.63; 95% CI:0.29-1.39; p = 0.25) and 5-year overall survival rate (48.3 vs. 58.6%; OR 0.67; 95%CI: 0.27-1.65; p = 0.38).

CONCLUSION

Stent-related perforation is associated with an increased risk of global and locoregional recurrence. The successful placement of the stent as a bridge to surgery in the curative purpose of patients with obstructed colon cancer does not exclude the presence of underlying perforation, with the consequent danger of disease spread. PROSPERO registration number: CRD42020152817.

An evidence for surface expression of an immunogenic epitope of sarcoplasmic/endoplasmic reticulum calcium-ATPase2a on antigen-presenting cells from naive mice in the mediation of autoimmune myocarditis

We recently reported identification of sarcoplasmic/endoplasmic reticulum calcium-ATPase2a (SERCA2a) 971-990, which induces atrial myocarditis by generating autoreactive T cells in A/J mice. However, it was unknown how antigen-sensitized T cells could recognize SERCA2a 971-990, since SERCA2a-expression is confined to an intracellular compartment. In this report, we present evidence that antigen-presenting cells (APCs) from lymphoid and non-lymphoid organs in naïve animals present SERCA2a 971-990 and stimulate antigen-specific T cells. Using major histocompatibility complex (MHC) class II dextramers for SERCA2a 971-990, we created a panel of T cell hybridomas and demonstrated that splenocytes from naïve A/J mice stimulated the hybridoma cells without exogenous supplementation of SERCA2a 971-990. We then recapitulated this phenomenon by using SERCA2a 971-990 -specific primary T cells, verifying that the T cell responses were MHC-restricted. Furthermore, SERCA2a 971-990 -sensitzed T cells exposed to APCs from naïve mice were found to produce the inflammatory cytokines interferon-γ, granulocyte macrophage colony stimulating factor, and interleukin-17A, which are implicated in the induction of myocarditis. Finally, while T cells exposed to mononuclear cells (MNCs) obtained from heart and liver also responded similarly to splenocytes, endothelial cells (ECs) generated from the corresponding organs displayed opposing effects, in that the proliferative responses were suppressed with the heart ECs, but not with the liver ECs. Taken together, our data suggest that the surface expression of SERCA2a 971-990 by naïve APCs can potentially trigger pathogenic autoreactive T cell responses under conditions of autoimmunity, which may have implications in endothelial dysfunction.

PD-1 expression is upregulated on adapted T cells in experimental autoimmune encephalomyelitis but is not required to maintain a hyporesponsive state

T cell adaptation is an important peripheral tolerogenic process which ensures that the T cell population can respond effectively to pathogens but remains tolerant to self‐antigens. We probed the mechanisms of T cell adaptation using an experimental autoimmune encephalomyelitis (EAE) model in which the fate of autopathogenic T cells could be followed. We demonstrated that immunisation with a high dose of myelin basic protein (MBP) peptide and complete Freund's adjuvant failed to effectively initiate EAE, in contrast to low dose MBP peptide immunisation which readily induced disease. The proportion of autopathogenic CD4⁺ T cells in the central nervous system (CNS) of mice immunised with a high dose of MBP peptide was not significantly different to mice immunised with a low dose. However, autopathogenic T cells in mice immunised with high dose MBP peptide had an unresponsive phenotype in ex vivo recall assays. Importantly, whilst expression of PD‐1 was increased on adapted CD4⁺ T cells within the CNS, loss of PD‐1 function did not prevent the development of the unresponsive state. The lack of a role for PD‐1 in the acquisition of the adapted state stands in striking contrast to the reported functional importance of PD‐1 in T cell unresponsiveness in other disease models.

Monophosphoryl Lipid A Enhances Efficacy of a Francisella tularensis LVS-Catanionic Nanoparticle Subunit Vaccine against F. tularensis Schu S4 Challenge by Augmenting both Humoral and Cellular Immunity

Francisella tularensis, a bacterial biothreat agent, has no approved vaccine in the United States. Previously, we showed that incorporating lysates from partially attenuated F. tularensis LVS or fully virulent F. tularensis Schu S4 strains into catanionic surfactant vesicle (V) nanoparticles (LVS-V and Schu S4-V, respectively) protected fully against F. tularensis LVS intraperitoneal (i.p.) challenge in mice. However, we achieved only partial protection against F. tularensis Schu S4 intranasal (i.n.) challenge, even when employing heterologous prime-boost immunization strategies. We now extend these findings to show that both LVS-V and Schu S4-V immunization (i.p./i.p.) elicited similarly high titers of anti-F. tularensis IgG and that the titers could be further increased by adding monophosphoryl lipid A (MPL), a nontoxic Toll-like receptor 4 (TLR4) adjuvant that is included in several U.S. FDA-approved vaccines. LVS-V+MPL immune sera also detected more F. tularensis antigens than LVS-V immune sera and, after passive transfer to naive mice, significantly delayed the time to death against F. tularensis Schu S4 subcutaneous (s.c.) but not i.n. challenge. Active immunization with LVS-V+MPL (i.p./i.p.) also increased the frequency of gamma interferon (IFN-γ)-secreting activated helper T cells, IFN-γ production, and the ability of splenocytes to control intramacrophage F. tularensis LVS replication ex vivo Active LVS-V+MPL immunization via heterologous routes (i.p./i.n.) significantly elevated IgA and IgG levels in bronchoalveolar lavage fluid and significantly enhanced protection against i.n. F. tularensis Schu S4 challenge (to ∼60%). These data represent a significant step in the development of a subunit vaccine against the highly virulent type A strains.

Self-reactivity as the necessary cost of maintaining a diverse memory T-cell repertoire

The adaptive immune system is expected to protect the host from infectious agents and malignancies, while avoiding robust activation against self-peptides. However, T cells are notoriously inept at protection whenever the pathogen or tumor is persistent in the body for longer periods of time. While this has been thought of as an adaptation to limit the immunopathology from continued effector T-cell responses, it is also likely an extension of the T cell's intrinsic mechanisms which evolved to tolerate self-peptides. Here we deliberate on how the need to tolerate self-peptides might stem from a paradoxical requirement-the utility of such molecules in maintaining a diverse repertoire of pathogen-specific memory T cells in the body. Understanding the mechanisms underlying this intriguing nexus, therefore, has the potential to reveal therapeutic strategies not only for improving immune responses to chronic infections and tumors but also the long-term efficacy of vaccines aimed at cellular immune responses.

Comparison of Long-Term Outcomes Between Emergency Surgery and Bridge to Surgery for Malignant Obstruction in Right-Sided Colon Cancer: A Multicenter Retrospective Study

BACKGROUND

Malignant obstruction in right-sided colon (MORC) has traditionally been treated by emergency resection with primary anastomosis. The aim of this study was to evaluate short-term postoperative and long-term oncologic outcomes according to the surgical approach adopted for MORC.

METHODS

A total of 1785 patients who underwent curative surgery for stage II or III colon cancer in seven hospitals were reviewed retrospectively. Seventy-four of 1785 patients had MORC. We compared the postoperative outcome and long-term oncologic outcome between the emergency surgery (ES) group (49 patients) and the bridge to surgery (BS) group (25 patients) for 74 patients with MORC.

RESULTS

There were no differences in the length of the distal and proximal resection margin (p = 0.820 and p = 0.620) or the number of metastatic lymph nodes (p = 0.221). There were no differences in flatus passage (p = 0.242), start of diet (p = 0.336), hospital stay (p = 0.444), or postoperative morbidity (p = 0.762). The 5-year overall survival rates were 73.2 % in the ES group and 90.7 % in the BS group (p = 0.172). Moreover, the 5-year disease-free survival rates were 71.9 % in the ES group and 76.2 % in the BS group (p = 0.929).

CONCLUSIONS

On the basis of the above results, the postoperative course of the ES group was similar to that of the BS group. In addition, the long-term oncologic outcome of the BS group was similar or slightly better than that of the ES group. BS after colonic stent may be an alternative option for MORC.

Immune Cells and Inflammation in Diabetic Nephropathy

Diabetic nephropathy (DN) is a serious complication of diabetes. At its core, DN is a metabolic disorder which can also manifest itself in terms of local inflammation in the kidneys. Such inflammation can then drive the classical markers of fibrosis and structural remodeling. As a result, resolution of immune-mediated inflammation is critical towards achieving a cure for DN. Many immune cells play a part in DN, including key members of both the innate and adaptive immune systems. While these cells were classically understood to primarily function against pathogen insult, it has also become increasingly clear that they also serve a major role as internal sensors of damage. In fact, damage sensing may serve as the impetus for much of the inflammation that occurs in DN, in a vicious positive feedback cycle. Although direct targeting of these proinflammatory cells may be difficult, new approaches that focus on their metabolic profiles may be able to alleviate DN significantly, especially since dysregulation of the local metabolic environment may well be responsible for triggering inflammation to begin with. In this review, the authors consider the metabolic profile of several relevant immune types and discuss their respective roles.

Functionally responsive self-reactive B cells of low affinity express reduced levels of surface IgM

Somatic gene rearrangement generates a diverse repertoire of B cells, many which have receptors possessing a range of affinities for self-Ag. Newly generated B cells express high and relatively uniform amounts of surface IgM (sIgM), while follicular (FO) B cells express sIgM at widely varying levels. It is plausible, therefore, that downmodulation of sIgM serves as a mechanism to maintain weakly self-reactive B cells in a responsive state by decreasing their avidity for self-Ag. We tested this hypothesis by performing comparative functional tests with FO IgM(hi) and IgM(lo) B cells from the unrestricted repertoire of WT C57BL/6 mice. We found that FO IgM(lo) B cells mobilized Ca(2+) equivalently to IgM(hi) B cells when the same number of sIgM molecules was engaged. In agreement, FO IgM(lo) B cells were functionally competent to produce an antibody response following adoptive transfer. The FO IgM(lo) cell population had elevated levels of Nur77 transcript, and was enriched with nuclear-reactive specificities. Hybridoma sampling revealed that these B-cell receptors were of low affinity. Collectively, these results suggest that sIgM downmodulation by low-affinity, self-reactive B cells preserves their immunocompetence and circumvents classical peripheral tolerance mechanisms that would otherwise reduce diversity within the B cell compartment.

Does use of a metallic colon stent as a bridge to surgery modify the pathology data in patients with colonic obstruction? A case-matched study

BACKGROUND

In a recent propensity score study, we established that overall- and disease-free survival were worse after use of a colonic stent (CS) than after emergency surgery for colonic obstruction. The present study sought to explain the association between CS use and poor survival by analyzing pathological specimens.

METHODS

From January 1998 to December 2011, all patients with left obstructive colon cancer and having been operated on with curative intent were included in the study. The primary end point involved a comparison of pathological data from the CS- and the surgery-only groups in a case-matched analysis (with the groups matched for the T stage). In a series of secondary analyses, we studied a range of factors known to be associated with adverse outcomes (microscopic perforation, vascular embolism, perineural invasion, and lymph node invasion) in the study population as a whole (in order to evaluate stenting as an adverse factor) and in the CS group alone (in order to identify factors associated with a poor prognosis in this specific group of patients).

RESULTS

A total of 84 patients were included in the study (50 in the CS group). Stenting was mentioned in only 70 % of the pathology lab reports (n = 35/50). Twenty-five patients in the CS group were matched with 25 patients of the surgery-only group. Tumor ulceration (p < 0.0001), peritumor ulceration (p < 0.0001), perineural invasion (p = 0.008), and lymph node invasion (p = 0.005) were significantly more frequent in the CS group. In a multivariate analysis of the CS group, T4 status and tumor size were significant risk factors for microscopic perforation, perineural invasion, and lymph node invasion.

CONCLUSION

The CS- and surgery-only groups differed significantly in terms of ulceration at or near the tumor, perineural invasion, and lymph node invasion. Explanation of the adverse outcomes associated with CS use will probably require further investigation.