Cells of the Immune System Flashcards
Cells of the immune system: - - -
- circulate in the bloodstream - migrate into tissues to detect foreign antigens - accumulate in specialised organs where they develop and differentiate
Name the types of white blood cells: - - - - -
- Monocytes - Eosinophils - basophils - Lymphocytes - Neutrophils
Where do all WBC come from? What can they divide into?
They all originate from a pluripotent haemopoietic stem cell found in bone marrow They can divide to form: - common lymphoid precursors - megakaryocytes - granulocytes down the myeloid lineage - mast cells - monocytes in blood which may migrate to become macrophages
What can common lymphoid precursors divide into? Where can all these lymphocytes migrate into?
Some migrate and emerge as B lymphocytes in the blood Others become NK cells in the blood Some go to the thymus and undergo differentiation and become T cells in the blood All these lymphocytes can migrate into the tissues and into secondary lymphoid tissues
What will megakaryocytes give rise to?
Megakaryotes will give rise to platelets in the blood
Where can macrophages arise from?
Further differentiation of monocytes from the blood, into the tissues Also from secondary lymphoid tissues
What cells are involved in the secondary lymphoid tissues? What do these cells have in common?
Macrophages, interdigitating cells, dendritic cells All these cells are antigen presenting cells
Briefly describe an antigen presenting cell
Very good at presenting antigen to other cells within the immune system
What does the lymphoid lineage give rise to and its function?
Lymphocytes: involved in recognition and effector function
What does the myeloid lineage consist of and the function of each cell type?
Granulocytes (short lived) - neutrophils - eosinophils - basophils all involved in effector cell function Monocytes: involved in recognition and effector functions, remove particulate matter
Facts about neutrophils - - - - -
- constitute ~95% of circulating granulocytes - 10-20 microns in diameter - characteristic multi-lobed nucleus - predominant role: phagocytosis and destruction of pathogens - adhere to endothelial cells and enter tissues (diapedesis)
What do neutrophils contain within their granules?
- lysosomes - acid hydrolases, myeloperoxidases, lysozyme and defensins Secondary granules - lactoferrin and lysozyme
What type of nucleus does eosinophils have? What do they stain with?
- Characteristic bilobed nucleus - Cytoplasmic granules stain with eosin
What does the crystalloid core of granules contain in eosinophils?
- Major basic protein = potent toxin for helminth worms - cationic protein - eosinophil derived neurotoxin
What can eosinophils do to large pathogens?
They are able to bring about the killing of pathogens too large to be phagocytosed
Basophils: - - -
- present in very small numbers in circulation - mast cells share characteristics with basophils but are only found in tissues - basophils have a segmented nucleus and large cytoplasmic granules
What triggers both mast cells and basophils? What effect does this have?
- Allergens which trigger the allergic response to release contents of their granules
Monocytes - -
- horse shoe shaped nucleus - many pinocytic vesicles and lysosomal granules
What do lysosomes contain? Why is this important?
Lysosomes contain peroxidase and acid hydrolases - important for killing phagocytosed micro-organisms
What is the major function of macrophages?
Disposal of microbes and dead body cells through phagocytosis
Give examples of accessory cells and their functions: - - - -
- platelets: involved in blood clotting and inflammation - antigen presenting cells: present antigen to T cells - mast cells - endothelial cells: receptors recognise certain lymphocytes - control lymphocyte traffic and distribution
What are the roles of monocytes, macrophages and antigen presenting cells in the immune response?
- phagocytosis, even clearing up dead neutrophils - concentrate antigen - process/present antigen to T cells - secrete growth factors, cytokines
What do we need for a strong immune response?
- Cooperation between B cells, T cells and APC - cell to cell contact - secretion of cytokines
What are lymphocytes required for?
Lymphocytes are involved in recognition and effector function
What are the key roles of lymphocytes?
- Both cellular and humoral immunity - circulate all around the body - found in blood, lymph and specialised tissues - some are long lived e.g. memory cells
Removal of lymphocytes results in: - -
- Inability to produce antibody - Inability to carry out cellular immunity
What are the primary lymphoid organs: - -
- bone marrow - thymus
Name some secondary lymphoid organs:
- spleen - lymph nodes - lymphoid nodules - waldeyer’s ring - bronchus associated lymphoid tissue - peyer’s patches - urogenital lymphoid tissue
Where do common lymphoid precursors go?
- 25% in bone marrow and differentiate further to become B cells - 60% in thymus, into T cells - 15% result in natural killer cells
What are cell markers?
- monoclonal antibodies are widely used to study cell surfaces - each mAb is highly specific for one antigenic determinant - Their use in experiments with immune cells has resulted in the development of a system of nomenclature: Cluster of Differentiation (CD) system
What are all lymphocytes?
All lymphocytes are antigen specific - specific for only one antigenic determinant - has a specific antigen receptor on its surface
Where is the specificity of lymphocytes acquired?
In the primary lymphoid organs: bone marrow and thymus
How are B and T cells activated?
By encountering the particular antigen, specific for that lymphocyte
What are B cells differentiated into? Cytotoxic T cells? Helper T cells?
B cells - plasma cells: factories for making immunoglobulin Tc cells - have granules containing proteins involved in killing Th cells - develop ability to produce growth factors or lymphokines
What does binding of antigen to lymphocyte antigen receptor trigger?
Triggers clonal selection and expansion of specific lymphocyte for that antigen
What is the key to adaptive immunity and why?
Clonal expansion which produces more activated and memory cells, therefore a more rapid, effective response
