DESCRIBE THE ROLE AND FUNCTION OF DIFFERENT CELL TYPES OF INNATE IMMUNITY

The immune system is a complex biological system that protects us from pathogenic organisms such as bacteria, viruses, fungi and the like derived from hematopoietic stem cells in the bone marrow. It includes leukocytes, chemicals and proteins such as complement proteins and antibodies. This system is divided into two main parts: innate immune system (nonspecific) and adaptive system (specific). Congenitality is the main defense mechanism and the adaptive immune system is the second line of defense, so congenital nature plays an important role in this system.

Innate immunity is the body's first line of defense. Following the identification of pathogens by the innate immune system, an important process involved in generating an effective immune response is the activation of adaptive immunity. Antigen presenting cells (APCs) are specific types of cells that play an important role in promoting this process. APC is a specific cell that breaks down protein antigens into peptides and presents these peptides on the cell surface by specific membrane bound glycoproteins called major histocompatibility complex (MHC) molecules. In man, the MHC molecule is called human leukocyte antigen (HLA).

Antigen presenting cells display antigens in the form of peptides on histocompatibility molecules. T cells selectively recognize antigens; different types of T cells will be activated depending on the type of antigen and histocompatibility molecules. For T cell receptor (TCR) recognition, peptides are processed into small fragments within cells and must be presented by major histocompatibility complex (MHC). Without the help of immunological adjuvants, antigens can not elicit immune responses. Likewise, the adjuvant component of the vaccine plays an important role in the activation of the innate immune system.

An immunogen is an antigenic substance (or adduct) capable of eliciting a humoral (congenital) or cellular immune response. It initially initiates an innate immune response and then induces activation of the adaptive immune response. When these antigens are generated, the antigen binds to a very diverse immune receptor product (B cell receptor or T cell receptor). Immunogens are those capable of inducing an immune response called immunogenicity. At the molecular level, the antigen is characterized by its ability to bind to the variable Fab region of the antibody. Different antibodies may distinguish specific epitopes present on the surface of the antigen. A hapten is a small molecule that alters the structure of an epitope. In order to induce an immune response it is necessary to attach it to a large carrier molecule such as a protein (a complex of peptides). Antigens are usually carried by proteins and polysaccharides, but lipids are less than that.