What is Immunity? Definition of Immunity Immunity is the body’s ability to resist or protect itself against harmful pathogens or diseases. What is Immune System? Lymphoid Organs Primary lymphoid organs Secondary lymphoid organs Tertiary lymphoid organs How does Immunity Work? Mechanism of Immunity Types of Immunity The primary purpose of the immune system is to … Read more
What is Precipitation Reaction? Precipitation Reaction Definition Precipitation reaction refers to a chemical reaction in which two soluble substances react to form an insoluble solid compound, known as a precipitate. This reaction occurs when two aqueous solutions containing ions combine, resulting in the formation of an insoluble product that settles out of the solution as … Read more
Activation of B cells requires two signals. Depending on the kind of antigen, B-cell activation occurs via two different pathways, one dependent on helper T cells (TH cells) and the other not. The connection between CD40 of B cells and CD40 ligand of T cells gives a second signal for T-dependent antigen, whereas cross-linking of … Read more
What are Superantigens (SAgs)? Superantigens (SAgs) are a type of antigens that stimulate the immune system excessively. It specifically results in non-specific T-cell activation, polyclonal T-cell activation, and large cytokine release. Superantigens are microbial or viral toxins that constitute a class of disease-associated, immunostimulatory substances and function as V-restricted, highly potent polyclonal T cell mitogens. … Read more
Antigen Processing and Presentation Foreign protein antigen recognition by a T cell needs the presentation of peptides produced from the antigen within the cleft of an MHC molecule on the cell membrane. The production of these peptide-MHC complexes requires the degradation of a protein antigen into peptides, a process known as antigen processing. The degraded … Read more
Antigen Presentation Definition Antigen presentation is the expression of antigen molecules on the surface of a macrophage or other antigen-presenting cell in conjunction with MHC class II molecules when the antigen is being presented to a CD4+ helper T cell or with MHC class I molecules when the antigen is being presented to a CD8+ … Read more
What is Antigen? Antigen Definition An antigen is a foreign molecule or substance that triggers an immune response in the body, leading to the production of antibodies. or An antigen is a substance that can stimulate an immune response in the body. It can be a molecule or a part of a molecule, such as … Read more
Antigen-Antibody (Ag-Ab) Interaction refers to the biochemical reaction that occurs between antibodies and specific antigens when they come into close proximity, typically within a distance of several nanometers. This interaction plays a critical role in the immune response against foreign substances and pathogens in the body. The binding of antibodies to specific antigens is facilitated … Read more
What is HLA Complex? The MHC in the human genome is known as the HLA complex (for human leukocyte antigen complex). The HLA complex encompasses approximately 3,500 kb on chromosome 6 and is composed of 12 main sections. Each region contains dozens of genes, of which only a few are functional and the majority do … Read more
MHC molecules serve to bind peptides and deliver them to passing T lymphocytes for examination. In the case of selfpeptides, T cells with a TCR capable of binding with high affinity to the peptide–MHC complex have likely been eliminated by the mechanisms of central tolerance or rendered non-responsive by peripheral tolerance. In the event of … Read more
The complement pathway or cascade is a component of the immune system that boosts the ability of phagocytic cells and antibodies to eliminate pathogens and damaged cells from an organism, stimulate inflammation, and assault the pathogen’s cell membrane. Both the innate and adaptive immune systems generate complement pathways. This system is comprised of tiny, inactive … Read more
An Overview of Complement System What is Lectin Pathway of Complement Activation? Components of Lectin Pathway 1. Mannose-binding lectin Structural subunits of mannan-binding lectin (MBL) and ficolins 2. MBL serum levels and MBL2 gene polymorphisms 3. Ficolins Ficolin-1 Ficolin-2 Ficolin-3 4. MBL-associated serine proteases Steps, Mechanism, Process of Lectin Pathway The lectin pathway, also known … Read more
What is Alternative pathway of the complement system ? Activators of the alternative pathway Activators of the alternative pathway of complement activation include Steps of activation of alternative pathway Four serum proteins comprise the initial component of the alternative pathway: C3b, factor B, factor D, and properdin. 1. C3bB complex Formation 2. C3bB Cleavage 3. … Read more
The classical pathway is a key immune system mechanism that plays an important role in defending the body from foreign invaders. It consists of a series of sequential interactions among complement components that result in the killing of target cells via a process known as cell lysis. The presence of an antibody attached to an antigen, … Read more
Through its role as a mediator, complement helps the humoral response become a potent defence mechanism that can eliminate pathogens. Other complement components or split products help with the inflammatory response, opsonization of antigen, virus neutralisation, and clearance of immune complexes in addition to the MAC’s role in mediating cell lysis. The binding of complement … Read more
Complement System Definition The complement system, also known as the complement cascade, is a component of the immune system that boosts the ability of antibodies and phagocytic cells to eliminate germs and damaged cells from an organism, stimulate inflammation, and assault the cell membrane of a pathogen. The complement system is an incredibly potent system … Read more
What is Immune Response? Immune Response is the mechanism through which the host’s immune system reacts to a damaging foreign particle or pathogen (antigen) in the body. It involves identifying the antigen and activating defence mechanisms against invading infections. Antigens are chemicals that are located on the surface of cells, viruses, bacteria, or fungi, and … Read more
What is the humoral immune response/What is humoral immune response? Humoral immunity definition Humoral immunity, also known as the humoral immune response, refers to the branch of the immune system that produces antibodies in response to extracellular pathogens and foreign substances, primarily mediated by B-lymphocytes and plasma cells in the body’s extracellular fluids. History The … Read more
Definition of Immunological Tolerance Immunological tolerance is a state of specific immunologic nonreactivity to a specific antigen to which an individual has been previously exposed. Immune tolerance stops the immune system from responding to self-antigens. Mechanisms of Tolerance The proposed mechanisms of tolerance are clonal deletion, clonal anergy, and suppression. Clonal deletion: Clones of B … Read more
Cell-Mediated Immunity Definition CMI is an unique sort of acquired immune response that is not mediated by antibodies but rather by sensitised T cells. This type of immunity is passed from donor to recipient without the need of antisera, but rather with intact lymphocytes; therefore, it is referred to as cell-mediated immune reaction. Contrary to … Read more
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