biology infectious disease/ the human immune system - year 11

be precise

what are the two types of immune systems?

innate and adaptive

what is the first, second and third line of defence?

innate: first and second

adaptive: third

what is the innate immune system?

•Non-specific: provides general defence against microbes.

•We are born with the ability to generate an innate immune response.

•It doesn’t adapt or change during our lifetime.

•First and second line of defence.

what is the adaptive immune system?

1.Adaptive immune system

•Specific defences that involve the immune system.

•Has the ability to retain memory of prior infections.

•Third line of defence.

what is the first line of defence?

The first line of defence includes physical, chemical and biological barriers that help prevent the entry of pathogens into the body.

what are biological barriers?

•Biological barriers involve the activity of various beneficial microorganisms that live on and inside the body.

•These compete with harmful pathogens for space and nutrients, preventing their growth and colonisation.

•Beneficial microorganisms can be found on the skin, in the gut, mouth, nose and urogenital openings.

what is the second line of defence?

•Triggered after the first line is penetrated and consists of internal defencesthat aim to slow the spread of or neutralize pathogens.

•Rapid, non-specific response that responds in the same manner for all pathogens.

Main responses of the second line of defence include:

•Inflammatory response

•Increased production of white blood cells (macrophages, neutrophils and natural killer cells)

•Fever: slightly high body temperature may limit the growth of microbes

•Complement system

describe white blood cells?

•White blood cells are also called leukocytes and generally form in the bone marrow.

•There are many different types of white blood cells.

•Some are non-specific in their action against pathogens and are part of the innate immune system, whereas others are specific in their action and part of the adaptive immune system.

what are the main white blood cells I need to know?

neutrophil, macrophages, mast cell

what is phagocytosis?

Steps of phagocytosis:

1. The white blood cell detects a pathogen.

2. It surrounds the pathogen with its cell membrane.

3. The pathogen is engulfed into a vesicle.

4. Enzymes break down and destroy the pathogen.

what does phagocytosis stand for? also what is phagocytosis a type of?

cell eating, and is a type of endocytosis

what are phagocytes?

•Phagocytes are a group of immune cells specialized in finding and "eating" bacteria, viruses, and dead or injured body cells.

•Three main types of phagocytes: neutrophils, macrophages and dendritic cells.

what are the main chemicals of the innate immune system?

•Cytokines are signaling proteins secreted by leukocytes and infected cells.

•Involved in communication between cells and assist in regulating inflammation and the immune response.

•Includes:

•Interferons: released by cells infected with viruses. They signal neighboring, uninfected cells to produce protective antiviral proteins, halting the spread of the virus.

•Interleukins: regulate inflammation, draw infection-fighting white blood cells to the affected area, and can trigger a fever to make the body less hospitable to pathogens

Chemokines:stimulate the migration of leukocytes to the site of infection.

what is the complement system?

•Current human complement system involves over 30 different proteins which are primarily produced by the liver.

•Found in blood plasma and tissue fluid.

•Have 3 main effector functions:

1.Bind to surface molecules on pathogens to attract phagocytes to the site of infection and enhance their identification for phagocytosis.

2.Binding to and puncturing holes in the pathogen cell’s membrane causing it to rupture.

3.Binding to mast cells and stimulating them to release histamine, which intensifies the inflammatory response.

what is the inflammatory response?

•The inflammatory response is the body’s immediate response to infection or injury aimed at containing damage, eliminating pathogens and initiating healing.

•When tissue is injured, damaged cells and local immune cells (like macrophages and mast cells) release chemical mediators such as histamine and cytokines.

•These signals cause blood vessels to dilate (vasodilation) and become more permeable, allowing specialized white blood cells like macrophages and neutrophils to enter the tissue, and eliminate pathogens via phagocytosis.

•These immune cells also release factors that promote repair like blood clotting factors that seal the wound and lead to the formation of a scab.

•This response also causes the cardinal signs of inflammation: heat, redness, pain and swelling.

what is a fever and how does it enhance the immune response?

•Abnormally high temperature in response to an infection.

•Normal body temperature is 37°C – an internal body temperature above 38 °C is considered to be a fever.

•Fever enhances the immune response by:

•Creating an environment less favourable for pathogens as elevated temperature inhibits the growth of many bacteria and viruses.

•Accelerating immune cell activity.

Improving the production of antibodies.

what is the adaptive immune response? (third line of defence)

•The adaptive (also known as the acquired) immune system is characterised by its specificity and ability to retain memory of prior infections.

•Lymphocytes are a type of white blood cell that play a central role in the adaptive immune response.

•Consists of two parts:

•Humoral response: counters extracellular pathogens

•Cell-mediated response: counters intracellular pathogens

what are MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) PROTEINS?

•MHC proteins are cell-surface markers that play a critical role in the immune system distinguishing self from non-self.

•They present antigens from pathogens or self-proteins to T lymphocytes, which are critical for initiating responses.

Two types:

•MHC Class 1 proteins

•MHC Class 2 proteins

what is the humoral immune response?

•Counters extracellular pathogens.

•Involves white blood cells called B lymphocytes (or B cells).

•2 types of B cells:

•Plasma cells: produce antibodies.

•Memory cells: help the immune system activate much faster if the same intruder invades again.

antibodies are produced and immune response is triggered, but the antibodies are produced in response to what?

•Antibodies are proteins which are produced in response to an antigen.

•Antibodies are specific for a particular antigen.

•Antigens can be:

•Pathogens or their toxins

•Pollen

•Blood cell surface molecules

•Proteins on transplanted tissue

what is the difference between primary and secondary response?

•The primary adaptive immune response occurs when the immune system encounters a pathogen for the first time.

•Slower as immature T and B cells are activated and antibodies are produced.

•Can take days to weeks to develop.

•The secondary adaptive immune response is faster, stronger and more specific due to the activation of memory B and T cells generated during the primary response.

what is the cell mediated immune response?

•Targets infected or abnormal cells.

•Involves white blood cells called T lymphocytes (T cells).

•2 types of T cell:

•Helper T cells: regulate the immune response, activate B cells and cytotoxic T cells.

•Cytotoxic T cells: specialised in attacking and killing infected cells and cancer cells.

•The cell-mediated response is initiated by antigen-presenting cells (APCs) presenting antigens on their surface using MHC class II molecules to helper T cells.