Cells of the Immune System
What are MHC complex molecules? And what is the human form called?
Major histocompatibility complex molecules which are proteins on APCs that present antigens to T cells split into classes I and II
Human Leukocyte Antigens (HLAs)
What are the 2 lymphoid organ tissues?
thymus --> produces T cells
bone marrow --> produce all other cells
What are the 1st, 2nd, and 3rd line defenses of the immune system called?
1st: External defense
2nd: internal defense
3rd: Specific/Acquired/Adaptive defense
What is the principal function of IgM immunoglobulins?
complement system activation
Define Atopy.
an increased susceptibility to develop hypersensitivity reactions
How do Natural Killer Cells function as part of the innate immune system?
-kill host cells infected by intracellular pathogens
-respond to IL-12 and secrete INF-gamma --> activating macros to kill phagocytized pathogens
-kill pathogens inside phagocytized cells
What are the 3 types of peripheral lymphoid organs?
-lymph nodes
-spleen
-mucosal and cutaneous lymphoid tissues
What is the reaction time difference between Non-specific and Specific Immunity mechanisms?
Non-specific: in the first 6-12 hours of infection
Specific: within 1-5 days after infection
What is the principal function of IgA?
mucosal immunity --> transporting IgA through epithelia (ex: mouth)
Explain how viral load is affected in both acute and chronic infections.
Acute infection has a high viral load due to CB8+ proliferation and differentiation into cytotoxic T cells and memory cells (viral clearance)
Chronic infection has consistent viral load and CD8+ initially respond but express inhibitory receptors that exhaust the T cells (viral persistence)
What are functions/characteristics of Dendritic cells?
-strong APCs
-involved in the innate and adaptive immune system
-secrete cytokines that activate NK cells
-differentiate CD4+ and CD8+ cells
-promote and suppress inappropriate autoreactive responses in autoimmune diseases
What is Lymphocyte Recirculation?
-T cells circulating in blood to give the immune system surveillance and vantage point
-Naive T cells: circulate through the peripheral lymphoid organs
-Effector/Mature T cells: circulate to the site of infection
What are the 3 functions of Epithelia in Innate Immunity?
-physical barrier
-produce antibiotics that kill pathogens
-kill microbes and infected cells by intraepithelial lymphocytes
What is Immunoglobulin Isotype Switching?
Immunoglobulins switching from a low class Ig to a high class Ig
-differentiating and switching to different isotypes to accommodate for more functions
What are the 2 types of inflammatory mechanisms that are active in Type II hypersensitivity?
Activation of complement system (Goodpasture)
Molecular Mimicry (rheumatic fever)
What are PRRs and what are their functions?
Pattern Recognition Receptors
-very important in inflammation
-directly recognize the pattern of bacteria on pathogens entering the body
What are 4 types of T cell-mediated diseases?
Diabetes Type 1, Contact Dermatitis, Multiple Sclerosis (MS), Inflammatory Bowel Disease
What are the 3 main functions of antibodies?
-Neutralize effect of microbes and toxins
-Opsonization and phagocytosis
-Activate the complement system
What is the primary function of IgE immunoglobulins?
-immunity against helminths (allergy reactions)
-mast cell degranulation (immediate hypersensitivity)
Which immune mechanism cells are used in all 4 types of Hypersensitivity?
Immediate type 1: produce IgE antibody
Antibody-mediated type 2: production of IgG and IgM
Immune complex-mediated type 3: deposition of antigen-antibody complexes --> complement activation
Cell-mediated type 4:activated T lymphocytes
What are the classes of lymphocytes and their functions?
B cells: in-charge of antigen recognition and activate the complement system
Helper T cells: (CD4+) activate effector T cells to release cytokines (activate macrophages and inflammation) and activating proliferation and differentiation of B and T cells
Cytotoxic T cells: (CD8+) kill infected cell once shown the microbial antigen
What kind of hypersensitivity is involved in joint inflammation and bacterial infections like chlamydia?
Type III hypersensitivity
What is the difference between T-dependent and T-independent immunoglobulin affinity maturation?
T-dependent: with use of helper T cells
-isotype switched high-affinity antibodies (memory B cells and long-lived plasma cells)
T-independent: without use of helper T cells
-mainly IgM, low affinity antibodies
-short-lived plasma cells
-no memory cells
What are the functions and characteristics of IgG?
-Fc receptor-dependent phagocyte responses
-complement activation
-neonatal immunity
subtypes (IgG1 and IgG3)
What is a classic example of Delayed Type Hypersensitivity (DTH)?
A PPD Test for tuberculosis
-intracutaneous injection of purified protein derivative (PPD, aka Tuberculin) which have protein antigens of Mycobacterium tuberculosis bacillus
-the reaction occurs in 8-12 hours, reaching a peak in 24-72 hours and then slowly subsides