2.4.2: Lines of defence Flashcards
what are the 3 lines of defence in a human
barriers -> non-specific immune system -> specific immune system
what is the difference between immunity and resistance
immunity occurs in response to an antigen and produces antibodies
resistance is when you are tolerant to an antigen and experience no harm
give 7 examples of barriers that humans have
skin
tears
sweat
saliva
stomach acid
mucus
flora
How does stomach acid act as a barrier
denatures proteins of cell membrane
how does mucus act as a barrier
by trapping pathogens before they can enter the lungs
what is flora and how does flora act as a barrier
flora - our body is covered in bacteria and fungi inside and out providing competition with other bacteria and fungi and therefore acting as a barrier
how do tears, sweat and saliva act as a barrier
all contain lysozymes, these digest murein of bacterial cell wall -> weaken the cell wall -> cell lysis during osmosis
what does skin contain that helps its role in acting as a barrier
collagen and keratin
describe how the non specific immune system carries out its role
blood clotting
phagocytosis
inflammation
describe the role of the T helper cell in the cellular response
identifies pathogen (antigen presentation), and then goes through the process of clonal selection (selecting a T cell with the complementary receptor to the antigen) and expansion (mitosis). Then the T helper cells release cytokine chemicals to stimulate cytotoxic T cells, B cells and macrophages/neutrophils. T helper cells also divide by mitosis to form memory cells
describe the process of antigen presentation in relation to a macrophage
macrophage engulfs pathogen by phagocytosis
engulfed pathogen’s antigen is broken down by lysosomes in the macrophage
macrophage then presents the antigen on its own surface
Describe the role of the cytotoxic T cells in the cellular response
Complementary cytotoxic T cells (clonal selection) bind to the antigen on antigen presenting cell and is activated OR is activated by the T helper cell
Clonal expansion - divide by mitosis to form memory cells and Tc cells
Tc cells bind to the antigens on the infected body cell, and release Perforin proteins into the cell’s membrane which creates a pore -> water and ions enter by osmosis -> cell lysis
Describe the role of the memory T cells in the cellular response
Remain in blood for decades, have the antigen memorised so that in the next exposure to the same antigen, the memory T cells can identify the same antigen quicker and carry out clonal expansion quicker (much less time spent on clonal selection)
Describe the role of B cells in the humoral response
B cells with a complementary antibody receptor bind to presented antigen -> clonal selection and clonal expansion -> some of the daughter cells differentiate into plasma B cells, others into memory B cells
Describe the role of plasma B cells in the humoral response
Plasma B cells secrete antibodies that specifically combine with the antigen that has entered the body deactivating/killing the pathogen
Plasma B cells are packed with RER (synthesis of antibodies), Golgi (package and secrete antibodies), Mitochondria (ATP for synthesis and exocytosis of antibodies)
