T and B lymphocytes Flashcards
What are antigens and what do they do?
Usually proteins that are recognised as foreign by the immune system + stimulates an immune response.
It triggers production of antibodies as part of body’s defence system
Where are antigens found?
Part of the cell-surface membranes of invading cells e.g microorganisms or abnormal body cells e.g cancer cells
What are lymphocytes produced by?
Stem cells in bone marrow
T cells mature in thymus gland + B cells mature in bone marrow
What are the two types of lymphocytes?
T and B lymphocytes
How can T lymphocytes distinguish invader cells from normal cells?
The invader cells e.g pathogens, virus, transplanted cells and cancer cells have different specific antigens on their cell-surface membranes
What are antigen-presenting cells?
Cells that display foreign antigens (from other cells) on their surface
What type of response are T lymphocytes involved in?
Cell-mediated immunity (cellular response)
What do T cells have on their surface and what do they do?
They have receptor proteins on their surface that detect specific (complementary) antigens
What are the two forms of T cell?
- Helper T cells
- Cytotoxic T cells
Describe the cell-mediated immune response
- After the pathogen is engulfed, the phagocyte presents the pathogen’s antigens on its surface (becomes antigen-presenting cell)
- Receptors on specific helper T cells bind to antigens on antigen-presenting cells (fits perfectly - complementary)
- This activates the T cells
Activated T cells:
- Divide by mitosis to produce T helper cell clones (they continue to circulate in the blood)
- Releases cytokines to activate T cytotoxic cells
- Activate B cells
- Stimulate phagocytosis
Describe what cytotoxic T cells do
- Produce perforin protein
- Makes holes in cell surface membrane
- Results in cell death
What type of lymphocytes are involved in cell-mediated immunity?
T lymphocytes
What type of lymphocytes are involved in humoral immunity?
B lymphocytes
What do B lymphocytes have on their surface?
They have antibodies on their surface
Describe the humoral immunity response
- The B cells with complementary antibodies engulfs the pathogen
- The antigens from the pathogen are presented on the B cell
- The activated helper T cells bind to the presented antigen using its complementary receptor protein
- B cells clone by mitosis - activated by T cells to divide
- Plasma cell clone is made to secrete antibodies
OR - Memory cells made, circulate in blood for future infections
What do the antibodies secreted by plasma cell clones do?
The antibodies attach to antigens and:
- Agglutinate (stick together in large clumps to target)
- Stop pathogens invading body cells
- Bind to free toxin proteins
What is the primary response (part of humoral immunity response)?
Antibodies are secreted
What is the secondary response (part of humoral immunity response)?
Memory cells are made
What do B cells produce?
Clones. Each clone produces one specific antibody - referred to as monoclonal antibodies
