CD4+ T cells Flashcards
What are CD4+ T cells?
Part of the adaptive immune system and key regulators of the immune response
What is the role of CD4+ T cells?
To recognize antigens presented by MHC Class II molecules and provide help to other immune cells
What is the link between dendritic cells and adaptive immunity?
Dendritic cells capture and process antigens and present them via MHC Class II molecules to CD4+ T cells
What changes occur in dendritic cells during activation?
Upregulation of MHC Class II co-stimulatory molecules like B7.1 and B7.2 and chemokine receptor CCR7
What is the primary function of cytokines produced by CD4+ T cells?
To organize and orchestrate the correct immune response to specific pathogens
What are the five subsets of CD4+ T cells?
Th1 Th2 Th17 Tfh follicular helper T cells and Treg regulatory T cells
What determines the differentiation of naive CD4+ T cells?
Cytokines produced by dendritic cells in response to pathogens activate specific transcription factors in T cells
What cytokines are produced by Th1 cells?
IFN gamma and TNF alpha to enhance cellular immunity
What cytokines are produced by Th2 cells?
IL4 IL5 and IL13 to enhance humoral immunity and antibody production
What cytokines are produced by Th17 cells?
IL17 to mediate responses against extracellular bacteria and fungi
What cytokines are produced by Treg cells?
IL10 and TGF beta to inhibit activation of other T cells and regulate immune responses
What is the function of Tfh cells?
To assist B cells in germinal centers by promoting class switching and high-affinity antibody production
How do cytokines regulate the differentiation of CD4+ T cells?
Cytokines activate STAT transcription factors which induce specific differentiation programs
What is the role of CD4+ T cells in activating CD8+ T cells?
CD4+ T cells stimulate antigen-presenting cells by upregulating co-stimulatory molecules like CD40 and secreting IL2 to activate CD8+ T cells
What is the Th1/Th2 balance?
The immune system’s ability to shift between Th1 responses for intracellular pathogens and Th2 responses for extracellular pathogens
What pathogens stimulate Th1 responses?
Viruses and intracellular bacteria stimulate Th1 responses
What pathogens stimulate Th2 responses?
Helminths and extracellular parasites stimulate Th2 responses
What role do Th17 responses play?
They mediate defense against extracellular bacteria and fungi
What are thymus-dependent TD antigens?
Protein antigens that require CD4+ T cell help to generate an antibody response
What are thymus-independent TI antigens?
Highly repetitive antigens like polysaccharides that can induce antibodies without CD4+ T cell help
How can CD4+ T cells contribute to disease?
Excessive Th1 Th2 or Th17 responses can cause autoimmune diseases while excessive Th2 responses can lead to allergies
What is the role of HLA Class II alleles in autoimmune diseases?
Certain HLA Class II alleles are linked to autoimmune diseases due to their involvement in CD4+ T cell activation
What is the significance of cytokine production by CD4+ T cells?
It drives the differentiation of other immune cells and tailors the immune response to specific pathogens
What is the importance of the immunological synapse?
It allows for precise interaction between antigen-presenting cells and CD4+ T cells for effective activation
What happens when CD4+ T cells are dysregulated?
Imbalances can lead to conditions like autoimmunity allergies or poor immune responses
