innate defences
- the bodys first line of defence against pathogens.
- non - specific
- respond quickly to a wide range of invaders such as physical barriers like skin , mucous membranes and imune cells such as macrophages and neutrophils which attack foreign substances.
- innate immmunity does not have memory so it reacts the same way a pathogen is encountered.
adaptive defences
- specific
- take longer to develop
- involve the activation of lymphocytes such as T cells and B cells which recognise speicifc antigens.
- has memory to remember past infections which leads to a faster and stronger response upon subsequent exposures to the same pathogen.
White blood cell / leukocytes
function - WBC defends the body against infections, identify and destroy pathogens such as bacteria, viruses and fungi. play roles in sllergic reactions and inflammation
mobility of WBC
highly mobile and can move through the blood stream and tissues to reach sites of infection, injury. they exit the b.ood vessels and migrate to areas where they are needed.
life span of WBC
neutrophils have a short lifespan - a few days
memory T cells can live for years providing long term immunity.
production of WBC
in bone marrow and can develop in lymphatic tissues, the increased production by the body is a reponse to infections or other immune challenges.
neutrophils
most number of WBC in the body as they are unable top leave the body unless at the site of an infection. §
lymphoid tissues
they monitor the body for signs & infections / disease making a rapid immune response when needed.
B cell activation - in secondary lymphoid tissues, B cells can encounter antigens become activated and diffferentiate into plasma cells that produce antibodies.
T cell activation - they encounter antigens in these tissues which leads to activation and clonal expansion.
filtration of lymph - nodes filter lymph fluid which traps pathogens & foreign particles which allows fpr destruction of immune cells.
Cytokines
small portions important for cell signalling. regulates immune reponses, inflammation and formation of blood cells.
they help activate and direct immune cells such as T cells and B cells which respond to infections/ injuries.
promote/ ihibit inflammation which is a crucial part of the immune reponse to pathogens
they serve as communication signals between cells allowing them to co ordinate their activities during an immune response.
Antibodies - igs STRUCTURE
made up of 4 polypeptide chains which consists of 2 heavy and 2 light chains which are binded by disulfide bonds. Y shaped structure
variable region is the tip of the antibody which is unique to each antibody- responsible to bind to specific antigens
constamt region is formed by the remaining part of the of the heavy and light chains which determines the class of the antibody and mediates its interactions with other componants of the immune system
Antibdodies Function
antigen binding - antibodies specificially recognise and bind to antigens which can be proteins, carbs or other molecules on the surface of pathogens
neutralization - antibodies can neutalize their ability to infect cells or interfere with their function
osponization - antibodies can coat pathogens, marking them for destruction by phagocytic cells such as macrophages and neutrophils.
complement fixation - some antibodies can activate the complement system , enhancing the ability of antibodies and phagoctic cells to clear microbes and damaged cells.
IgG
IgA
IgM
IgE
IgD
Helper T cells
- start the immune reponse
- do not directly kill infected cells but help activate other immune cells such as B cells and cytotoxic T cells.
- recognize antigens presented by antigen 0 presenting cells and secrete cytokines to stimulate immune repsonse.
Cytotoxic T cells
kills infected or cancerous cells.
recognise and bind to cells which display foreign antigens on their surface leading to the destruction of target cells.
throughthe release of perforin abd granzymes which induce apoptosis.
Reulatory T cells
- play a criticial role in mainataining immune tolerance and preventing autoimmune diseases.
- help regulate and suppress the immune repsonse so the body does not attack its own tissues.
- they can inhibit the activity of other T cells and promote the survival of self - tolerant cells.
Memory T cells
after an infection has been cleared some T cells become memory T cells.
- they stay in the body for a long period of time and provide a faster and more robust response upon re - exposure to the same antigen.
- Memory T cells can be either CD4+ or CD8+ and crucial long - term immunity.
Natural killer T cells
recognise lipidantigens presented by CD1d molecules and can rapidly produce cytokines, contributing to the immune repsponse against infections and tumours
B cell activation
occurs in the bone marorw incolves stafes of pro - B cells to matue B cells.
- activation involves antigen recognition, co - stimulation from T cells and cytokine signalling leading to differentitation into plasma cells and memory B cells.
natural passive immunization
- occurs naturally
- when a mother transfers antibodies to her baby through the placenta during pregnancy or through breast milk after birth.
- helps protect the newborn from infections during the early month of life
artificial passive immunisation
transfer of antibodies from one individual to another, providing immediate but temporary protection against diseases
