Chemokine (C-C Motif) Receptor 2 Mediates Dendritic Cell Recruitment to the Human Colon but Is Not Responsible for Differences Observed in Dendritic Cell Subsets, Phenotype, and Function Between the Proximal and Distal Colon.

BACKGROUND & AIMS: Most knowledge about gastrointestinal (GI)-tract dendritic cells (DC) relies on murine studies where CD103+ DC specialize in generating immune tolerance with the functionality of CD11b+/- subsets being unclear. Information about human GI-DC is scarce, especially regarding regional specifications. Here, we characterized human DC properties throughout the human colon. METHODS: Paired proximal (right/ascending) and distal (left/descending) human colonic biopsies from 95 healthy subjects were taken; DC were assessed by flow cytometry and microbiota composition assessed by 16S rRNA gene sequencing. RESULTS: Colonic DC identified were myeloid (mDC, CD11c+CD123-) and further divided based on CD103 and SIRPα (human analog of murine CD11b) expression. CD103-SIRPα+ DC were the major population and with CD103+SIRPα+ DC were CD1c+ILT3+CCR2+ (although CCR2 was not expressed on all CD103+SIRPα+ DC). CD103+SIRPα- DC constituted a minor subset that were CD141+ILT3-CCR2-. Proximal colon samples had higher total DC counts and fewer CD103+SIRPα+ cells. Proximal colon DC were more mature than distal DC with higher stimulatory capacity for CD4+CD45RA+ T-cells. However, DC and DC-invoked T-cell expression of mucosal homing markers (ß7, CCR9) was lower for proximal DC. CCR2 was expressed on circulating CD1c+, but not CD141+ mDC, and mediated DC recruitment by colonic culture supernatants in transwell assays. Proximal colon DC produced higher levels of cytokines. Mucosal microbiota profiling showed a lower microbiota load in the proximal colon, but with no differences in microbiota composition between compartments. CONCLUSIONS: Proximal colonic DC subsets differ from those in distal colon and are more mature. Targeted immunotherapy using DC in T-cell mediated GI tract inflammation may therefore need to reflect this immune compartmentalization.

Prognostic Value of the Tumour-Infiltrating Dendritic Cells in Colorectal Cancer: A Systematic Review.

Dendritic cells (DCs) either boost the immune system (enhancing immunity) or dampen it (leading to tolerance). This dual effect explains their vital role in cancer development and progression. DCs have been tested as a predictor of outcomes for cancer progression. Eight studies evaluated tumour-infiltrating DCs (TIDCs) as a predictor for colorectal cancer (CRC) outcomes. The detection of TIDCs has not kept pace with the increased knowledge about the identification of DC subsets and their maturation status. For that reason, it is difficult to draw a conclusion about the performance of DCs as a predictor of outcome for CRC. In this review, we comprehensively examine the evidence for the in situ immune response due to DC infiltration, in predicting outcome in primary CRC and how such information may be incorporated into routine clinical assessment.

Impact of tailored feedback in assessment of communication skills for medical students.

BACKGROUND: Finding out the effective ways of teaching and assessing communication skills remain a challenging part of medication education. This study aims at exploring the usefulness and effectiveness of having additional feedback using qualitative analysis in assessment of communication skills in undergraduate medical training. We also determined the possibilities of using qualitative analysis in developing tailored strategies for improvement in communication skills training. METHODS: This study was carried out on medical students (n=87) undergoing their final year clinical performance examination on communication skills using standardized patient by video-recording and transcribing their performances. Video-recordings of 26 students were randomly selected for qualitative analysis, and additional feedback was provided. We assessed the level of acceptance of communication skills scores between the study and nonstudy group and within the study group, before and after receiving feedback based on qualitative analysis. RESULTS: There was a statistically significant increase in the level of acceptance of feedback after delivering additional feedback using qualitative analysis, where the percentage of agreement with feedback increased from 15.4 to 80.8% (p<0.001). CONCLUSIONS: Incorporating feedback based on qualitative analysis for communication skills assessment gives essential information for medical students to learn and self-reflect, which could potentially lead to improved communication skills. As evident from our study, feedback becomes more meaningful and effective with additional feedback using qualitative analysis.