“ Immunity is Immunity involves both Other components ofbasically a biological specific and non-specific the immune systemterm that describes a components. The non-specific adapt themselves to state of having components act either as each new diseasesufficient biological barriers or as eliminators of encountered and are defenses to avoid wide range of pathogens able to generateinfection, disease, or irrespective of antigenic pathogen-specific other unwanted specificity immunitybiological invasion ”
There are 2 types of Immunity1) Adaptive Immunity2) Innate Immunity.
Cell-mediated immunity is an immune response that does not involve antibodies or complement but rather involves the activation of macrophages, natural killer cells (NK), antigen-specific cytotoxic T- lymphocytes, and the release of various cytokines in response to an antigen. The second arm of the immune response is refered to as Cell Mediated Immunity (CMIR). As the name implies, the functional "effectors" of this response are various immune cells.
These functions include: Phagocytosis and killing of intracellular pathogens Direct cell killing by cytotoxic T cells Direct cell killing by NK and K cells
While the production of antibody through the humoral immune response can effectively lead to the elimination of a variety of pathogens, bacteria that have evolved to invade and multiply within phagocytic cells of the immune response pose a different threat.The following will aid in its Explanation :1) Extracellular microorganisms Non-encapsulated microorganisms are easily phagocytosed and killed within macrophages. Encapsulated microorganisms require the production of antibody in order to be effectively phagocytosed. Once engulfed, however, they are easily killed.
2) Intracellular microorganisms Intracellular microorganisms elicit the production of antibody, which allows effective phagocytosis. Once engulfed, however, they survive within the phagocyte and eventually kill it. Intracellular microorganisms also activate specific T- cells, which then release lymphokines (e.g. IFN, TNF) that cause macrophage activation. Activated ("killer") macrophages are then very effective at destroying the intracellular pathogens.
The second half of the cell-mediated immune response is involved in rejection of foreign grafts and the elimination of tumors and virus-infected cells. The effector cells involved in these processes are cytotoxic T-lymphocytes (CTLs), NK-cells and K-cells. Each of these effector cells recognizes their target by different means, described below :1) Cytotoxic T-lymphocytes:
1) T Helper cells (TH cells) 2) Cytotoxic cells (Tc cells or CTLs) 3) Memory T Cells. 4 Regulatory T cells .
1) T helper cell(TH cells) assist other white blood cells in immunologic processes, including maturation of B cells into plasma cells and activation of cytotoxic T cells and macrophages, among other functions. 2)Cytotoxic T cells (TC cells, or CTLs) destroy virally infected cells and tumor cells, and are also implicated in transplant rejection
3) Memory T cells are a subset of antigen-specific T cells that persist long-term after an infection has resolved. They quickly expand to large numbers of effector T cells upon re-exposure to their cognate antigen, thus providing the immune system with "memory" against past infections. Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells Regulator).
4) Regulatory T cells (Treg cells) formerly known as suppressor T cells, are crucial for the maintenance of immunological tolerance. Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction and to suppress auto-reactive T cells that escaped the process of negative selection in the thymus.
2) NK(Natural killer) cells: NK cells are part of a group known as the "large granular lymphocytes". These cells are generally non- specific, MHC-unrestricted cells involved primarily in the elimination of Neoplastic or tumor cells The precise mechanism by which they recognize their target cells is not clear. Probably, there is some type of NK-determinant expressed by the target cells that is recognized by an NK-receptor on the NK cell surface. Once the target cell is recognized, killing occurs in a manner similar to that produced by the CTL.
3) K-cells: K-cells are probably not a separate cell type but rather a separate function of the NK group. K-cells contain immunoglobulin Fc receptors on their surface and are involved in a process known as Antibody-dependent Cell-mediated Cytotoxicity (ADCC). ADCC occurs as a consequence of antibody being bound to a target cell surface via specific antigenic determinants expressed by the target cell. Once bound, the Fc portion of the immunoglobulin can be recognized by the K-cell. Killing then ensues by a mechanism similar to that employed by CTLs. This type of CMIR can also result in Type II hypersensitivities.
Explanation of above Diagram Stimulation of immune response by activated helper T cells activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, TH1 and TH2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.
COMPONENTS AND FUNCTIONS OF THE COMPLEMENT SYSTEM The complement system found in the blood of mammals is composed of heat labile substances (proteins) that combine with antibodies or cell surfaces. This complex, multicomponent system is composed of about 26 proteins. The "complement cascade" is constitutive and non-specific but it must be activated in order to function. The functions of complement include: Making bacteria more susceptible to phagocytosis Directly lysing some bacteria and foreign cells Producing chemotactic substances
Increasing vascular permeability Causing smooth muscle contraction promoting mast cell degranulation . HypersensitivityHypersensitivity (also called hypersensitivity reaction) refers to undesirable (damaging, discomfort- producing and sometimes fatal) reactions produced by the normal immune system. Hypersensitivity reactions require a pre-sensitized (immune) state of the host.
It is classified into five different types1) Allergy2) CytoToxic Anti-Body dependent3 )Immune complex Disease4) Delayed type Hypersensitivity Response5) Auto-Immune Disease.Only type IV of Hyper Sensitivity is related to this topic . . Because its chemical mediators are T-cells
Cell-Mediated ImmunityPrepared by : Farrukh NadeemYasir Yaqoob : Talha Ahmed : Arnold Raffique.