Interferons that limit the spread of virus from cell to cell.
This is done by binding to nearby cells to induce the production of substances that inhibit viral reproduction.
Complement proteins interact with each other to either kill the pathogen directly or facilitates phagocytosis or induce inflammatory responses.
Antimicrobial peptides eliminate pathogens by binding to the carbohydrates structures found on the cell surface membranes of microbes to disrupt CSM or cell wall
- they have toll-like receptors to bind to fragments of molecules on the pathogens.
- these fragments of molecules otherwise known as PAMPs are unique to different pathogens
- binding of receptors to PAMPs activate phagocytic cells to induce phagocytosis
Natural Killer Cells release cytotoxic chemicals that lead to cell death of pathogen, thus inhibiting further spread of infection.
1. Macrophages and neutrophiles release cytokines to enhance immune system so as to promote blood flow
2. Mast cells near the connective tissues at the site of infection release histamine which cause the nearby blood vessels to dilate, increasing permeability of the blood vessels
3. Hence, the dilation of vessels and increase blood flow allows more phagocytic cells to be attracted to the infected tissues to carry out phagocytosis
4. Accumulation of pus at the site of infection
5. Increased blood flow due to dilated blood vessels results in redness, increase in skin temp and swelling
Saliva, tears etc has a washing action that inhibits the colonisation of fungi, bacteria on epithelial surfaces
- Lysozymes present in these secretions break down the peptidoglycan of the cell walls of bacteria.
Acidic pH environment in stomach, skin caused by secretions by oil and sweat glands that prevent growth of bacteria.
- Randomly select on copy from the multiple copies of V and J gene segment.
- There is only one copy of C segment.
- V(D)J Recombinase join the V gene segment to the J gene segment, thus forming the VJ gene segment.
- Separated from the C gene segment by an intron. Hence intron removed after transcription by RNA splicing to form a mature mRNA transcript.
- Translation to form the variable and constant regions of the light chain of B cells antigen receptor.
- Randomly select one V, J and D gene segment from the many copies of gene segment of V, J and D.
- D is joined to J first and the DJ segment is then joined to the V gene segment by V(D)J recombinase.
- Intron separate the C and VDJ gene segment.
- RNA splicing after transcription remove the intron
- Translation forms the variable and constant regions of the heavy chain.
Further diversifying of antibody molecules through the pairing of the variable regions of light and heavy chain to form antigen binding site.
- Occurs in the heavy chain of activated B cells
- Changes the constant regions of the heavy chain thereby allowing for the production of antibodies of different classes to be produced (lg D, A and E)
- lg D and M are the first antigen receptors to be expressed while lg M is always the first antibody to be produced.
- However, since the v regions remain unaffected, this remains the antigen specificity because it does not change the ABS
- This results in different effector functions upon binding of antibody to specific antigens.
- Point mutation is introduced to the rearranged VJ and VDJ regions of the light and heavy chain.
- These mutation occur at very heavy rate.
- Somatic hypermutation occur in activated B cells and is catalysed by activation induced cytidine deaminase.
- This causes a slightly altered amino acid sequence of the variable regions, hence either increasing or decreasing the affinity of the antigen binding site to the antigen.
- Those with increased affinity of the ABS will be allowed to mature and differentiate into antibody secreting plasma cells. (AFFINITY MATURATION)