Med I: Immunology Overview

Function Immune system

PREVENT or limit infections through a variety of defenses

Components of immune system

Both:

• NK T cell

• y6 T cell

Innate components:

COMPONENTS

• DENDRITIC CELL

• MAST CELL

• MACROPHAGE

• GRANULOCYTES (NK cell, Complement protein, basophil, eosinophil, neutrophil)

Adaptive components:

• B-CELLS AND T-CELLS

• ANTIBODY MEDIATED AND T-CELL MEDIATED IMMUNITY

first line of defense: barrier formed by intact skin and mucous membranes

second line: rapidly detect foreign material and destroy harmful agents

above are active before infectious exposure (INNATE)

third line: targeted defense that is specific for individual infectious agents

cell-mediated arm (T lymphocytes) and humoral arm (circulating factors, antibodies and cytokines)

above is the ADAPTED (aquired). takes time to become fully functional

Innate Immunity

nonspecific defenses that are encoded in genes prior to exposure to microbes

Rapid (w/in min) NO MEMORY

ex

• cell mediated (NK natural killer cells, macrophages)

• humoral (antibodies produced by B cells)

Functions

killing invaders and activating adaptive immunity

another imp function is to heal damaged tissue and clear away dead cells in a way that doesn’t harm body

barriers (e.g. skin and mucous membranes)

Adaptive Immunity

Highly specific

slow- requires several days before becoming affective

T-cells (cell-mediated immunity) VS B-cells (/humoral/antibody-mediated immunity)

B and T lymphocytes

Adaptive Immunity

Features of B cell

• humoral mediated immunity

• cell surface receptors for pathogens are immunoglobulins (each B cell expresses a single type of B cell receptor)

• mature in bone marrow into plasma cells (plasma cells secrete antibodies against pathogens)

• play a role in presenting antigens and cytokine secretion

Features of T cells

• Cell mediated immunity

cell surface receptors for pathogens are T cell receptors (each T cell expresses single type of T cell receptor)

• mature in the thymus

• rely on MHC

• named by CD markers on their surface

Active Immunity

host immune response induced after contact with foreign antigens (e.g., microorganisms)

can occur through infection or an immunization with microbial toxins or antigens

resistance is long-term through formation of memory

Natural → Infection

• ex. chickenpox

disadvantage: possibly fatal

Artificial → Vaccination

• ex. vaccine

disadvantage: not immediate reactions to vaccine

Passive Immunity

Given in the form of immune components that were preformed in another person or animal in response to a specific antigen

advantage of fast availability of large amts of antibody. however, short durability

Natural → Maternal antibodies

Artificial → Monoclonal antibodies (lab-made protiens)

Immunogen

Substance that is able to provoke an adaptive immune response if injected on its own (means that the molecule is immunogenic)

Types

• Antigen: immunogenic; any substance that body can recognize as foreign and use to trigger immune response

• Haptens: small molecule that can react with specific antibody. cannot start an immune response on its own. Only when covalently bound to a “carrier protein

• Adjuvants: Enhance the immune response to an immunogen, but do so without binding to antibody or to the immunogen

  • ex. can act by causing slow release of immunogen, prolonging stimulus etc

Immunity in Age

Newborn

not born with fully developed natural barriers

• IgG and IgA production begins AFTER birth reaches productivity at 1 year

• baby relies on maternal IgG (crosses placenta and would over before birth) and IgA secreted into breast milk

• vaccine schedules are not a guess. timed carefully so that baby can mount an effective response

Elderly

• lose immunity over time

• related to thymus atrophy and the loss of new T cells that can recognize new antigens

• can blunt responses to infection as well as vaccines

• Immunoscenescene - again immune system; ntural and gradual change to immune system as ppl age. body mount weaker response