NURB 3050 Immunity

Immune response

The collective, coordinated response of the cells and molecules of the immune system

What are the types of immune defenses

• innate

• Adaptive

Innate immunity

• the natural resistance with which a person is born with

• Reacts to foreign substance

• Limited to groups of microbes

Adaptive immunity

• the second line of defense

• Responds less rapidly but MORE effectively

• Able to recognize and react to a large number of microbes and nonmicrobial substances

• “Remember” the pathogen by quickly producing heightened immune response

• Being exposed to chicken pox

What is the defense for innate immunity

• epithelium (skin, mucous membranes)

• Phagocytes, inflammation, fever

What is the defense for adaptive immunity

• immunologic memory: more rapid and efficient with subsequent exposure

What are the cellular components of innate immunity

• phagocytes (monocytes/macrophages, neutrophils)

• NK cells

• DCs

What are the cellular components of adaptive immunity

• t lymphocytes

• B lymphocytes

• Macrophages

• DCs

• NK cells

What are the mediators of the Immune System

• cytokines

• Chemokines

• Colony-stimulating factors

Cytokines

• Soluble proteins secreted by cells of both the innate and adaptive immunity

• Bind to specific cells they target then activate the intracellular or phagocytosis

Chemokines

• Cytokines that stimulate the migration and activation of immune and inflammatory cells

• Help leukocytes migrate to site of injury

Colony-stimulating factors

Stimulate the growth and differentiation of bone marrow progenitors of immune cells

Interleukins (ILs)

• produced by macrophages and lymphocytes

• Primary function is to enhance the acquired immune response or regulate it through suppression or enhancement of the inflammatory process

Interferons (IFNs)

• primarily protect the host against viral infections

• Key role in the modulation of the inflammatory response

Tumor necrosis factor alpha (TNF-a)

• one of the most important mediators of the inflammatory process

• Key role it the detection of microorganisms

Lymphocytes

• Cells that specifically recognize and respond to foreign antigens

• T cells and B cells find antigens, eliminate pathogens, and destroy infected cells

Accessory cells

• macrophages and dendritic cells

• Function as antigen-presenting cells by the processing of a complex antigen into epitopes required for the activation of lymphocytes

• Engulf and digest

What are the innate recognition systems

• pattern recognition receptors (PRRs)

• Pathogen-associated molecular patterns (PAMPs)

• Toll-like receptors (TLRs)

Opsonins

• facilitation of phagocytosis

• Coat negatively charged particles on membranes

• Acute-phase reactants, lectins, complement proteins

Acute-phase proteins

• mannose-binding ligand and C-reactive protein

• Lab often checked to determine inflammatory response

The Complement system

• major mediator of inflammatory response

• Consists of proteins in the ECF

• Increases vascular permeability

• Increases bacteria aggregation (clumping)

• Lysis foreign cells

• Localize infection/destroy invading microbes

Adaptive immunity ___ when innate activates

Activates

Antigens

Substances foreign to the host that can stimulate an immune response

Antibodies

• receptors on immune cells

• Secreted proteins

• Recognize antigen, try to get rid of it

What are the types of antigens

• bacteria

• Fungi

• Viruses

• Protozoa

• Parasites

• Nonmicrobial agents (plant pollen, venom)

Humoral Immunity

• mediated by the molecules in the blood

• Principle defense against EXTRACELLULAR microbes and toxins

• Think B-lymphocytes

Cell-mediated immunity

• mediated by T-lymphocytes

• INTRACELLULAR microbes such as viruses

What are the structures of the immune system

• bone marrow

• Lymph nodes

• Thymus

• Spleen

• Tonsils

IgG

• most abundant

• Displays antiviral, antitoxin, and antibacterial properties

• Responsible for protection of newborn

IgA

• Predominant Ig in body secretions, protects mucous membranes

• Saliva, tears

IgM

• forms natural antibodies

• Prominent in early immune responses

• If elevated, person is developing antibodies in immune response

IgD

• found on B lymphocytes

• Needed for maturation of B cells

IgE

• binds to mast cells and basophils

• Involved in parasitic infections, allergic and hypersensitivity reactions

Class 1 MHC molecules

Virtually all nucleated cells

Class 2 MHC molecules

Restricted to immune cells, antigen-presenting cells, B cells, and macrophages

Antigen presentation

• macrophages and dendritic cells process and present antigen peptides to CD4+ helper T cells

• Capture antigens and then enable their recognition by T cells

• Initiation of adaptive immunity

B cells

• humoral immunity

• Memory

• Getting rid of extracellular microbes

T cells

• cell-mediated immunity

• Memory

• Getting rid of intracellular microbes

What are the factors of B lymphocytes

• presence of membrane immunoglobulin that functions as the antigen receptor

• Class II MHC proteins

• Complement receptors

• Specific CD molecules

What is the function of T lymphocytes

• activation of other T and B cells

• Rejection of foreign tissue grafts

• Delayed hypersensitivity reactions

• Control of intracellular viral infections

Active immunity

• specific protection induced following the exposure to antigens

• Immunizations

Passive immunity

• specific protection induced through the transfer of protective antibodies against an antigen

• Transferred from ANOTHER source

• Maternal IgG crosses the placenta to protect newborn before born

The elderly immune system is different from young adults by

• decline in immune responsiveness

• Decrease in size of thymus gland

• Biological clock in T cells

• Altered responses of the immune cells to antigen stimulation