Describe step-by-step what happens when a person gets a bacterial infection thro

Question

Describe step-by-step what happens when a person gets a bacterial infection through the skin cut and compare it to the step-by-step process of the viral infection.

For both of them start with the innate immune system and finish with the adaptive immune system (production of antibodies and memory cells).

Include terms such as: MHC-I, MHC-II, IL-1, IL-2, endogeneous, exogenous, native antigen, CD4+, CD8+, APC (antigen presenting cell), CTL, apoptosis, plasma cell, memory cells, phagocytosis, diapedesis, perforin/ granzyme, TCR, etc.

I am so lost in terms of this difference! I would appreciate some help, especially if you could break it down into pieces! Thank you!!!!

Explanation / Answer

Recognition of a foreign protein antigen by a T cell requires that peptides derived from the antigen be displayed within the cleft of an MHC molecule on the membrane of a cell, requiring the protein antigen be degraded into peptides by a series of events called antigen processing. The degraded peptides then associate with MHC molecules within the cell interior, and the peptide-MHC complexes are transported to the membrane, where they are displayed and the process is called antigen presentation.

This is an important aspect of the immune system involving multiple players.

The attachment of antigenic fragments to class 1 MHC or class 2 MHC molecules depends on the route thatthe antigen takes to enter a cell.

1. EXOGENOUS ANTIGEN PRESENTATION.

This occurs in case of Bacteria where the antigen is produced outside the hosr cell and enters the cell by endocytosis or phagocytosis. Antigen presenting cells (APC) like B-cells, macrophages dendritic cells etc,degrades the ingested antigen into fragments by the endolytic or phagocytic pathway.

The process is as follows

2.ENDOGENOUS ANTIGEN PRESENTATION.

This is for viral antigenic proteins synthesised by virus infected cell and uniquv proteins synthesized by cancerous cells.

The process is as follows

The B cell waits for the TH cell to bind to the MHC peptide complex, and after binding the activated TH cell releases cytokines inducing B cells to divide rapidly which make thousands of identical clones of B cell which either become plasma cells or memory cells.

The memory B cells remains inactive here, later when these memory B cells encounter the same antigen due to reinfection, they divide and form Plasma cells. On the other hand the plasma cells produce a large number of antibodies which are released free in the circulatiory system.

The invation by antigen triggers the complement system - a biochemical cascade of the innate immune system which aids to clear the pathogen from the body of an organism. It is derived from many small blood plasma proteins that work together to disrupt the target cell's plasma membrane leading to cytolysis of the cell.
The complement system is involved in the activities of both innate immunity and acquired immunit consists of more than 35 soluble and cell-bound proteins, 12 of which are directly involved in the complement pathways.The proteins account for 5% of the serum globulin fraction and circulate as inactive zymogens.
Activation of the complement system leads to chemotaxis, cytolysis and apoptosis, opsonization, immune clearance, and inflammation, as well as tagging of pathogens and antigens for phagocytosis.

So a general pathway would be

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