Exam questions 18, 19 Flashcards
Innate immune cell types and roles
Macrophages: Phagocytose microbes and debris, present antigens, and release cytokines. Dendritic cells: Capture and process antigens, present antigens to T cells, linking innate and adaptive immunity. Neutrophils: Phagocytose pathogens and release bactericidal substances. NK cells: Kill virus-infected and cancerous cells via lytic granules. Mast cells: Release histamine and other inflammatory mediators, promoting allergic reactions and parasitic defense.
Complement system activation pathways
Classical: C1q binds antibody-antigen complexes. Lectin: Mannose-binding lectin binds microbial carbohydrates. Alternative: Spontaneous C3 hydrolysis or C3b binding to pathogens.
C5 cleavage in complement system
C5a: Inflammatory mediator, recruits immune cells. C5b: Initiates membrane attack complex (MAC) formation, leading to pathogen lysis.
Pattern-recognition receptors (PRRs) families
TLRs, NLRs, CLRs, RLRs, CDSs.
PRRs sensing double-stranded RNA
RIG-I/MDA5: Cytosolic, signals through MAVS, induces IFN-β and antiviral responses. TLR3: Endosomal, signals through TRIF, induces IFN-β and antiviral responses.
Naïve CD4+ T helper cell activation
Antigen-presenting cells present antigens via MHC II to CD4+ T cells, initiating signaling through TCR and CD4 co-receptor.
CD4+ T cell subsets and cytokines
IL-12 + IFN-γ: Th1 IL-6 + IL-23: Th17 IL-4: Th2 TGF-β + IL-2: Treg IL-6: Tfh
Main functions of CD4+ T helper subsets
Th1: Activates macrophages, fights intracellular pathogens. Th17: Inflammation, defense against bacteria and fungi. Th2: Helps in parasitic immunity and antibody production. Treg: Suppresses immune responses, maintains tolerance. Tfh: Supports B cell activation and antibody production.
Licensing dendritic cells to activate CD8+ T cells
Dendritic cells present extracellular antigens via MHC I, providing co-stimulatory signals to activate CD8+ T cells.
Viral evasion via TAP inhibition
Inhibition of TAP prevents MHC I antigen presentation, impairing CD8+ T cell activation, but enhances NK cell-mediated killing.
Cytotoxic T cells, NK cells, NKT cells recognition
Cytotoxic T cells: Recognize antigens on MHC I. NK cells: Detect absence of MHC I or antibody-coated targets. NKT cells: Recognize lipid antigens presented on CD1d.
V(D)J recombination enzymes
RAG1/2: Initiates recombination at signal sequences. TdT: Adds random nucleotides, increasing diversity.
Follicular B2 cell activation and linked-recognition
B2 cells bind antigen, present it on MHC II to T helper cells. Linked-recognition requires T cell and B cell to recognize the same antigen.
AID processes and antibody effects
Somatic hypermutation (SHM): Introduces mutations in variable region, improving affinity. Class switch recombination (CSR): Changes antibody isotype for specialized functions.
Antibody isotypes
IgM, IgD, IgG, IgA, IgE.
Antibodies promoting phagocytosis
Antibodies activate complement (C3b), opsonize microbes for phagocyte recognition.
FcεRI signaling mutation effects
Impaired IgE signaling increases susceptibility to parasitic infections and reduces allergic reactions.
Monoclonal vs polyclonal antibodies
Monoclonal: Specific to one epitope, from a single B cell clone. Polyclonal: Recognize multiple epitopes, from multiple B cells.
Secondary/acquired immunodeficiency
Caused by external factors, such as infections (e.g., HIV) or cancer.
Herd immunity
Protection occurs when a large portion of the population is immune, reducing disease spread.
Immune response phases toward infection
Innate: Rapid, involves antimicrobial proteins, phagocytes, complement, and NK cells. Adaptive: Involves T and B cell activation, differentiation into effector cells, and memory formation.
Phagocytosis process and phagocytes
Phagocytosis: Engulfing pathogens into phagosomes for degradation. Neutrophils: Rapid responders, kill pathogens via granules. Macrophages: Resident cells, phagocytose pathogens, present antigens.
Role of C3 in immune response
C3 is essential for complement activation, opsonization, inflammation, and pathogen lysis. C3 deficiency: Increased susceptibility to bacterial infections and inability to form MAC.
Dendritic cells bridging innate and adaptive immunity
Dendritic cells capture pathogens and present antigens to T cells, providing co-stimulatory signals to initiate adaptive immunity.
MHC I and MHC II expression and antigen loading
MHC I: Expressed on all nucleated cells, presents intracellular antigens to CD8+ T cells. MHC II: Expressed on professional APCs, presents extracellular antigens to CD4+ T cells.
Positive selection of thymocytes and self-MHC restriction
Positive selection: Thymocytes that bind self-MHC with moderate affinity survive and differentiate. Self-MHC restriction: T cells recognize antigens only when presented by self-MHC molecules.
AIRE mutation and autoimmune disorders
AIRE allows tissue-specific antigen presentation in the thymus for self-tolerance. Its loss leads to autoimmune diseases.
HIV infection and CD4+ T cell loss
Loss of CD4+ T cells impairs adaptive immunity, leading to susceptibility to infections and loss of effective immune responses.
Th1 characteristics and role in immune response
Induced by IL-12 and IFN-γ, Th1 cells produce IFN-γ, activating macrophages for intracellular pathogen destruction.
Hematopoietic stem cells
Hematopoietic stem cells give rise to all blood cells, with self-renewal and multipotency abilities.
Antibody diversity in B2 cells
Combinatorial diversity, heavy-light chain pairing, P-nucleotide addition, exonuclease trimming, N-nucleotide addition by TdT.
Class-switch rearrangement importance
Enables antibodies to perform specialized functions by switching isotypes like IgG, IgA, and IgE.
IgM vs IgA structure and function
IgM: Pentameric, efficient complement activation, cannot cross placenta. IgA: Predominant in mucosal secretions, neutralizes pathogens without complement activation.
Types of vaccines and their advantages/disadvantages
Live attenuated: Pro - Strong immune response, fewer boosters. Con - Risk of reversion. Inactivated: Pro - Safe, stable storage. Con - Requires boosters, weak cell-mediated immunity. Subunit: Pro - Safe, stable. Con - Requires adjuvants and boosters.
