Innate immunity
Diverse array of cellular and subcellular components w/ which an individual is BORN.
Characteristics: antigen nonspecific, raid response (minutes-hours), no memory
Immune components: natural barriers (skin, mucous membranes), phagocytes and natural killer cells, soluble mediators (complement), pattern recognition molecules
Immunity
All the mechanisms used by the body as protection against environmental agents that are foreign to the body.
Acquired immunity
Only in vertebrates.
Characteristics: antigen specific, slow response (days), memory
Immune components: lymphocytes, antigen recognition molecules (b- and t- cell receptors), secreted molecules (antibody).
Memory response
Individual acquires the immunity to withstand and resist a subsequent attack by or exposure to the same offending agent.
Vaccination
Process of inducing acquired immunity. (vaccinia, from the Latin word vacca, meaning cow)
Antigen
Compound that induces the acquired immune response.
Active immunization
Immunization of an individual by administration of an antigen
Passive immunization
Immunization through the transfer of specific antibody from an immunized individual to a non immunized individual
Adoptive immunization
Transfer of immunity by the transfer of immune cells
Major characteristics of the acquired immune response
Specificity: ability to discriminate among different molecular entities and to respond only to those uniquely required, rather than making random, undifferentiated response.
Adaptiveness: respond to previously unseen molecules that may in fact never have been naturally existed before on earth.
Discrimination between self and non-self: cardinal feature - it is the ability to recognize and respond to molecules that are foreign and to avoid making this response to those molecules that are self.
Memory: a property shared with the nervous system it is the ability to recall previous contact with a foreign molecule and respond to it in a learned manner that is with a more rapid and larger response. Aka anamestiv response.
Antigen presenting cells (APC)
such as macrophages and dendritic cells constitute the third cell type participating in the acquired immune system. Although these cells do not have antigens specific receptors themselves they process and present antigen to the antigen specific receptors expressed by T cells.
Major histocompatibility complex (MHC)
Encoded by a set of polymorphic genes expressed within a population.
Colonial selection theory
- T and B lymphocytes of myriad specificities exist before there is any contact with the foreign antigen.
- Lymphocytes participating in an immune response express antigen specific receptors on their surface membranes. B cell receptors are the very molecules that subsequently get secreted as antibodies following b-cell activation.
- t cells have receptors denoted as T cell receptor. T cell products are not the same as their surface receptors instead other protein molecules called cytokines participate in the elimination of the antigen.
- each lymphocyte carries on the surface receptor molecules of only a single specific city this is true for both b and T cells.
Epitope or antigenic determinant
Surface receptors of the immunocompetent, lymphocytes combined foreign antigen.
With B-cell clones this process will lead to the synthesis of antibodies having specificity for the same antigen. The collective response produces an antiserum that is made up of antigen specific antibodies.
Each selected T cells will be activated to divide and produce clones with specificity for the same antigen.
Humoral immunity
b-cell-mediated
Cellular immunity
t-cell-mediated
Immunoglobulin
Immunoglobulins have common structural features which enables them to do two things: (1) recognize & bind specifically to a unique structural entity of the antigen - that epitope. (2) perform a common biologic function after combining with the antigen.
Consist of two identical light chains and two identical heavy chains linked by disulfide bridges. The portion of the molecule that binds antigen consist of an area composed of the amino terminal regions of both H and L chains.
5 immunoglobulin classes: based on differences in H chains.
IgG, IgM, IgA, IgE, IgD.
IgG is the only class of immunoglobulin that crosses the placenta conferring the mother’s community on the fetus.
IgA is the major anti-body found in secretions such as tears and saliva.
It is important to remember that antibodies in all five classes may possess precisely the same specificity against an antigen, while at the same time having different functional biological effector properties.
B-cell help
TH cells cooperate with B cells to enhance the production of antibodies. TH cells function by releasing cytokines which provide various Activation signals for the B cells.
Inflammatory effects
On activation certain TH cells release cytokines that induce the migration and activation of monocytes and macrophages leading to an inflammatory reactions.
Cytotoxic effects
Certain T cells called T cytotoxic cells are able to deliver a lethal hit on contact with their target cells leading to their death. Cd8+ cells.
Regulatory effects
TH1 cells can negatively cross regulate TH2 cells and vice versa. Another population of regulatory or suppressor T cells coexpresses CD4 and a molecule called CD 25.
Cytokine effects
Cytokines produced by each of the T cell subsets principally TH cells exert numerous effects on many cells lymphoid and non-lymphoid.
