Antigen

a substance (usually foreign) that binds specifically to an antibody (or) a T-cell receptor, often is used as an synonym for “Immunogen”.

(or)

An organism (or) a macromolecule, which stimulates a specific immune response, is called an “Immunogen” or “antigen”.

The molecular properties of antigens and the way these properties ultimately contribute to immune activation to our understanding of the immune system.

Immunogenicity:

Immunogenicity is the ability to induce a humoral and /or cell-mediated immune response.

B-cells + Antigen –>  Effector B-cells (plasma cells) + Memory cells

T-cells + Antigen –> Effector T-cells + Memory cells

Although a substance that induces a specific immune response is usually called an “antigen”, is more approximately called on “Immunogen” (Immune response inducing substance).

Antigenecity:

It is the ability to combine specifically with the final products of the above responses (i.e., antibodies and/or cell surface receptors). Although all molecules that have the property of immunogenicity also have the property of antigenicity, the reverse is not true.

Haptens: Low molecular weight molecules that can be made immunologic by conjugation to suitable carrier. These lake immunogenicity. Haptens are antigenic but not immunogenic. Haptens are incomplete antigens.

Popular posts from this blog

Null cells

Null cells are lymphocytes with cytotoxic properties. They are neither B-cells not T cell. They are intermediate between T and B cells. They form less than 3%. There are two types of Null cells namely, Natural Killer Cells (NK cells) and Killer Cells . Natural Killer Cells: NK cells are a group of null cells. They form the third population of lymphocytes. The NK cells have 2 or 3 large granules in the cytoplasm. Hence they are also Large Granular Lymphocytes (LGL). They have a kidney shaped nucleus. The NK cells kill the target cells without the aid of antibody or complement. So they are antibody independent. They destroy the cancer cells and cells infected with herpes and mumps virus . They are activated by Interferons and I nterleukins-2. Killer Cells (K cells): Killer cells are antibody dependent. These cells possess Fc receptors for binding with IgG antibodies. Hence they can bind with cells coated with IgG antibodies and can kill them. These cells can combine
Read more

Lymph node

Image
Lymph nodes are encapsulated bean-shaped structures containing a reticular network placed with lymphocytes, macrophages & dendritic cells. The overall architecture of a lymph node supports an ideal micro environment for lymphocytes to effectively encounter and respond to trapped antigens. The lymph node can be divided into three roughly concentric regions based on morphology: Cortex: The Cortex contains lymphocytes (mostly B-cells), macrophages & follicular dendritic cells arranged in primary follicles. This cortex region some times referred to as "Thymus-independent area. Medulla: It is innermost layer of lymph node P ara-cortex: Beneath the cortex, which is populated largely by T-Lymphocytes and also contains interdigitating dendritic cells thought to have migrated from tissues to the node. These interdigitating dendritic cells express high levels of class n MHC molecules, which are necessary for presenting antigen to T H -cells. These paracort
Read more

Thymus

Image
The thymus is a flat, bi-lobed organ situated above the heart. Immature T-cells are simply referred as "Thymocyte", these are densely packed outer compartment (or) cortex of the thymus lobule. Some of the thymic epithelial cells in the outer cortex, called "nurse cells", have long membrane extensions that surround as many as so thymocytes, forming large multicellular complexes The average weight of the thymus is 70 grams in infants; its age dependent involution levels an organ with an average weight of only 3 grams in the elderly. Explanations about Thymus: The thymus covered by a fibrous capsule . It is formed of two lobes. Each lobe of the thymus is organized into lobule which is separated from one another by septa called trabeculae. With in each lobule, the cells are arranged into an outer cortex and an inner medulla. The cortex is tightly packed with proliferating immature lymphocytes while the medulla contains more mature cells. As
Read more