Immune mecahnism of body against bacterial infection

 

May preserve these notes if you are aspiring for PhD after completion of MD(Gynae).

Q.1: What is the general principle of any immune reaction? :-On which sites of body a pathogen attacks first??  Ans : Pathogens are recognized and detected via pattern recognition receptors (PRR). These receptors are structures on the surface of macrophages which are capable of binding foreign invaders and thus initiating cell signalling within the immune cell.

Q,2: What dose bacteria contains??Ans: It is  pathogen-associated molecular patterns (PAMPs) .  Specifically, the PRRs identify pathogen-associated molecular patterns (PAMPs) which are integral structural components of pathogens. Examples of PAMPs include the peptidoglycan cell wall or LPS, both of which are essential components of bacteria and are therefore evolutionarily conserved across many different bacterial species.

 Q 3: What does macrophage do? When a foreign pathogen bypasses the physical barriers and enters an organism, the PRRs on macrophages will recognize and bind to specific PAMPs. This binding results in the activation of a signalling pathway which allows for the transcription factor NF-κB to enter the nucleus of the macrophage and initiate the transcription and eventual secretion of various cytokines such as Il-8, Il-1, and TNFα. Release of these cytokines is necessary for the entry of neutrophils from the blood vessels to the infected tissue. Once neutrophils enter the tissue, like macrophages, they are able to phagocytize and kill any pathogens or microbes.

 Q.4: What is complement ? Complement, another component of the innate immune system, consists of three pathways that are activated in distinct Pathogens are recognized and detected via pattern recognition receptors (PRR). These receptors are structures on the surface of macrophages which are capable of binding foreign invaders and thus initiating cell signalling within the immune cell.

Once neutrophils enter the tissue, like macrophages, they are able to phagocytize and kill any pathogens or microbes.

Complement, another component of the innate immune system, consists of three pathways that are activated in distinct ways. Each of the three pathways ensures that complement will still be functional if one pathway ceases to work or a foreign invader is able to evade one of these pathways.

Adaptive[edit]

MHC peptide presentation along with co-stimulatory ligand/receptor binding

Q. 5: What are adaptive immune response?  The adaptive immune response is the body's second line of defense. The cells of the adaptive immune system are extremely specific because during early developmental stages the B and T cells develop antigen receptors that are specific to only certain antigens. This is extremely important for B and T cell activation. B and T cells are extremely dangerous cells, and if they are able to attack without undergoing a rigorous process of activation, a faulty B or T cell can begin exterminating the host's own healthy cells.

 Activation of naïve helper T cells occurs when antigen-presenting cells (APCs) present foreign antigen via MHC class II molecules on their cell surface. These APCs include dendritic cells, B cells, and macrophages which are specially equipped not only with MHC class II but also with co-stimulatory ligands which are recognized by co-stimulatory receptors on helper T cells. Without the co-stimulatory molecules, the adaptive immune response would be inefficient and T cells would become anergic. Several T cell subgroups can be activated by professional APCs, and each T cell is specially equipped to deal with each unique microbial pathogen. The type of T cell activated and the type of response generated depends, in part, on the context in which the APC first encountered the antigen. Once helper T cells are activated, they are able to activate naïve B cells in the lymph node. However, B cell activation is a two-step process. Firsty, B cell receptors, which are just IgM and IgD antibodies specific to the particular B cell, must bind to the antigen which then results in internal processing so that it is presented on the MHC class II molecules of the B cell. Once this happens a T helper cell which is able to identify the antigen bound to the MHC interacts with its co-stimulatory molecule and activates the B cell. As a result, the B cell becomes a plasma cell which secretes antibodies that act as an opsonin against invaders.

Specificity in the adaptive branch is due to the fact that every B and T cell is different. Thus there is a diverse community of cells ready to recognize and attack a full range of invaders.^[7] The trade-off, however, is that the adaptive immune response is much slower than the body's innate response because its cells are extremely specific and activation is required before it is able to actually act. In addition to specificity, the adaptive immune response is also known for immunological memory. After encountering an antigen, the immune system produces memory T and B cells which allow for a speedier, more robust immune response in the case that the organism ever encounters the same antigen again.

ways. Each of the three pathways ensures that complement will still be functional if one pathway ceases to work or a foreign invader is able to evade one of these pathways.