Day 7 · CD4/CD8 and Regulatory T Cells

Session-1: Prof. Carla Rothlin, Yale School of Medicine

Signaling Pathways and Regulatory T cells

Goals:

Continue understanding the necessity of innate immunity for adaptive immunity.

Molecular Responses in Dendritic Cells to Bacteria Uptake:

Dendritic cells process bacteria via Toll-like receptors, initiating signal 1 (MHC II), signal 2 (CD80/CD86), and signal 3 (cytokines) to activate CD4 T cells.
CD4 T cells differentiate into T-helper 1 (Th1) for bacterial infections and Th2 for helminth infections.
Th2 responses involve cytokines like IL-4, triggering mucus production, peristalsis, and activation of eosinophils and mast cells.

Differentiation in Th1 and Th2 Responses:

Th1 response involves TBET transcription factors while Th2 response involves IRF4 for bacterial and helminth infections, respectively.
Dendritic cells activate specific T cell types based on infections via different signal pathways.

Cross-Presentation:

Epithelial cell-derived antigens are cross-presented by dendritic cells to activate both class I and class II MHC pathways, enabling CD8 and CD4 T helper cell activation, respectively.

Session 2: Prof. Siddharth Jhnjunwala, Department of Bioengineering, IISc

Importance of Immune Tolerance

Goals for Achieving Immunoregulation:

Preventing immune reactions against self and commensal microbes.
Initiating immune regulation mechanisms to maintain homeostasis.

Regulation of Immune Responses:

Thymic selection deletes T cells reacting against self-antigens.
PAMPs and DAMPs influence innate immune cells’ functions, whereas cytokines and transcription factors contribute to internal regulation.
Modulatory receptors like CTLA-4 and PD-1 help in immune regulation.

External and Internal Regulation:

Balancing self-regulation, external regulation, and costimulation influences the immune response.
Multiple mechanisms are employed to regulate immune responses, including inducing T cell death, suppressing T cell response, and inducing T cell anergy.

Q&A Session: Global Immuno Talk

Profs. Ann Rothstein and Neil Silverman

Drosophila Model for Studying Innate Immunity

Neil Silverman

Why Study Drosophila Immunity?

Significance:

Insects like Drosophila thrive without an adaptive immune system despite facing various infections.
Drosophila exhibits multiple defense mechanisms such as structural barriers, phagocytosis, RNAi, autophagy, and antimicrobial peptides.

Antimicrobial Peptides in Drosophila:

Various antimicrobial peptides like diptericins, attacins, drosocin, cecropins, defensins, metchnikowin, and drosomycins play vital roles in immunity.

Drosophila’s resilience against infections without adaptive immunity and its diverse defense mechanisms make it an intriguing model for studying innate immunity.