What is immunology?

·      Immunology is the study of a hosts reaction, when exposed to a foreign substance

·    it is the ability of an organism to distinguish SELF from NONSELF

What is immunity?

·      This refers to all the mechanisms used in the body as protection against environmental agents to the body

·      More simply, it is the condition of being resistant to infection.

What is innate immunity?

·      Innate (also called natural) immunity refers to the array of cellular and subcellular components with which is individual is BORN

Examples: skin, mucous membranes, cough reflex, pH, complement system, fever, interferons, phagocytic cells, and pattern recognition molecules

Name the 3 characteristics that differ innate from adaptive immunity.

Innate:

antigen nonspecific

rapid response(min-hours)

no memory

Acquired:

antigen specific

slow response (days)

Memory

Definition of Antigen

Any foreign material specifically bound by either antibodies or lymphocytes (a foreign molecules which initiates activation of the immune system) 

·      Active immunization:  immunization of an individual by administration of an antigen

What is passive immunization?

·      Passive immunization: immunization through the transfer of specific antibody from an immunized to an unimmunized individual. 

·      Adoptive immunization: transfer of immunity by the transfer of immune cells

·      Specificity: to respond to those uniquely required rather that making a random, undifferentiated response

·      Adaptiveness: the ability to respond to previously unseen molecules 

·      Discrimination between self and nonself:  the ability to respond to molecules that are foreign to the host and to avoid making a response to molecules that are self

·      Memory:  ability to recall a previous contact with a foreign molecule and respond to it in a more rapid and larger response that when it first encountered it! This is also called the ANAMNESTIC RESPONSE.

What are antigen presenting cells (APC)

·      Antigen-presenting cells: such as macrophages and dendritic cells, do not have sites on them which are antigen-specific, they process and present them to T-cells

What are Major histocompatibility complex (MHC) molecules?

molecule expressed by APC that are encoded by a set of polymorphic genes expressed within a population.

*determine sucess or failure of organ/tissue transplants

Name two cells that are invold in both acquired and innate immunity

Neutrophils and Mast cells

What BCR?

B-cell receptors. when attached to an antigen, are activated to form antibodies against that antigen.

Also gets secreted as antibodies following Bcell activation

What is TCR?

T- cell receptor site.    instead of producing antibodies, they produce chemicals called cytokines which help eliminate the antigen by regulating the cells needed to mount an effective immune response.

What is polyclonal antiserum?

Why is B cell immunity humoral?

 is called humoral immunity because it involves responses which use circulating free antibodies

·      T-cell immunity is called cell mediated immunity as it involves T-cell but not antibodies

What are Tc Cytotoxic cells?

·      are able to deliver a lethal hit on contact with their target cells, leading.  

What are Th (T helper Cells)

(Th) produce molecules called CD4 which are co-receptor (TCR) with an antigen-presenting cell (APC)

What is an antigen?

 An antigen is any agent capable of binding specifically, to parts of the immune system such as BCR’s 0n B lymphs or on to antibodies

What is an immunogen?

    an immunogen is any agent capable of inducing an immune response and is therefor, immunogenic

Are all immunogen antigens? vice versa?

Yes all immnogens are antigens

but no not all antigens are immunogens

What are haptens?

low-molecular weight compounds by themselves are incapable of initiating the immune response, but if conjugated to a larger agent , such as a protein, called the CARRIER the new high molecular weight compound, IS capable of immunogenesis

what are the 4 characteristics  a substance must have in order to be immunogenic?

1. foreignness

2. high molecular weight

3. chemical complexity

4. degradability

  the more foreign a substance is, the more immunogenic it is. There are expectations in which one mounts an immune response to their own tissues (R.A. , Lupus, etc…)

    compounds of  a molecular weight less than 1000 Daltons, are usually not immunogenic, between 1000 and 6000 may or may not be and those of greater than 6000 Daltons usually are

  a certain amount of chemical complexity is needed for immunogenicity, for instance a simple polymer of the amino acid lysine, although of high molecular weight would not be sufficient for immunogenicity.

More complex= more immunogenic

How does degradibility contribute to immunogenicity?

before they can express antgenic epitopes on surface APC must degrade antigen by antigen processing

once degraded and bound to MHC, epitopes, stimulate the activation and clonal expansion of antigen specific effector T cells

Which is the most common and most important immunogen?

proteins

Name a few other factors that may determine immunogenicity

 -individuals genotype-genes in  MHC

-lacking particular clone of lymphocyte 

-dosage 

-route of administration

01.      antigens administered subcutaneously generally elicit the strongest responses because Langerhans cells in the skin are among the most potent APC’s

02.      intravenously administered antigens are carried first to the spleen where they can induce immune unresponsiveness or, if presented by APC, induce a response

03.      orally administered antigens (GI) elicit local antibody responses but often produce a systemic state of tolerance

04. administration of antigen via the respitory tract (intranasal) 

What is primary response?

   The first exposure of an individual to an immunogen is referred to as the primary immunization, which generates a primary response.

What is seconday response?

1.      the second exposure to the same immunogen produces a secondary response.
2. much quicker in onset then in the first and of much stronger response.
3. occurs as if the body remembered it had been exposed to that antigen.
4. this second response is also called the memory or anamnestic response
5. the B and T cells that participate in it are called memory

What is the portion of the immunoglobulin that binds to the antigen part and is found in several hypervariable regions .....

What is an epitope? paratope?

epitope is antigen binding site (on AG)

paratope is antibody binding site (on AB)

What does a T cell need in order to interact with antigens?

The interaction of an epitope with the TCR, requires APC to process the antigen. 

Carbohydrates

Lipids

Nucleic Acids 

Proteins

Why can polysaccharides activate T cells on their own?

bc they cannot be processed by  APC so they only have epitopes for  B-cells

** can become part of a more complex molecule to elicit T cell responses**

How immunogenic are lipids?

  lipids are rarely immunogenic. Can be regarded as haptens. They can be immunogenic when conjugated to a carrier.

How immunogenic are nucleic acids?

    Nucleic acids are poor immunogens by themselves but become so when conjugated to proteins

How immunogenic are proteins?

Because virtually all proteins are immunogenic, the greater the complexity of the protein the greater the immune Reponses. These will contain multiple epitopes

Are Ab Ag binding forces covalent?

the binding of antigens to antibody is not covalent, they are weak forces. (non covalent bonding, hydrogen bonds, electromagnetic forces)

What is a toxoid?

toxin that has been modified and no longer toxic but has some of its immmuno chemical characteristics

(biologic activity destroted without affecting immunotgenicity)

Toxoid cross reacts with toxin

immunogenic reaction which the immune components (cells or AB) react with 2 different molecules that share epitopes but other wise dissimilar

another type --- ab or cells with specificity to one epitope bind, more weakly, to another epitope that is similar but not identical

     homologous antigen means that the antigen used to induce an immune reaction is the same as the one with which the induced immune components are then allowed to react.

(Antigen and immunogen are the same)

What is an heterologous antigen

What is an adjuvant?

     an adjuvant is a substance that, when mixed with an immunogen, enhances the immune response

**  an adjuvant is not a hapten a hapten only becomes immunogenic when binded to a carrier an adjuvant will not enhance a hapten

How does an adjuvant work?

 an adjuvant works by

1. increasing the half-life of the vaccine antigens

2. increasing inflammatory productions,

3. improving antigen delivery and antigen processing and APC presentation.