RBC/WBC Detail Flashcards
What are leucocytes and what are the types?
White cells which defend body against infection and participate in immune response. Are of 5 types in blood: 3 known as granulocytes as cytoplasm contains granulocytes, lymphocytes and platelets derived from megakaryotes.
What are the different granulocytes and how are they identified?
Depending on colour of granules in cytoplasm in stained blood film. Neutrophils = small lilac. Eosinophils = large orange. Basophil = large purple. Have lobulated or polymorphous nuclei so called polymorphonuclear leucocytes. Function mainly in tissue and reach by migrating through endothelium of capillary.
What are neutrophils and how do they reach pathogen target?
Neutrophils are phagocytic cells that respond to chemotactic stimuli by migrating to site of infection, inflammation or death and spend 7 hours in circulation. Process involves rolling along endothelium, adhering to specific endothelial receptors, diapedesis (moving through capillary wall) and migrating through tissue in response to chemotaxins.
How do neutrophils act within the tissue?
Pseudopodia flows around particles followed by fusion where bacterium enclosed in phagocytic vacuole in cytoplasm and garnules of neutrophil containing proteolytic enzyme and myeloperoxidase discharge into vacuole. Proteolysis of contents occur.
What is the function of eosinophils?
Defence against parasitic infection. Less efficient than neutrophil against bacteria. Also have unwanted actions when involved in allergic reaction.
What is the function of basophils?
Defence against parasite and allergic reactions.
Describe lymphocytes and different types
Lymphocytes are smaller than granulocytes and some contain cytoplasmic granules. Circulating lymphocytes look very similar to one another but are mainly of three lineages: B-cells, T-cells and NK cells. B-cells of bone marrow origin and migrate to lymph nodes and lymphoid tissue upon maturation. T-cells of bone marrow origin but migrate to thymus where they mature and then migrate to lymphoid tissues. NK cells part of body’s innate immune response.
How do B-cells act?
Exposed to antigen-presenting cells in lymphoid tissue where they undergo somatic mutation and cells most capable of recognising antigen survive and mature into memory B-cell and plasma cell. Exit from bloodstream through high endothelial venules of lymph nodes and post-capillary venules of other tissues.
How do T-cells act?
Diverse subsets of T-cells where some function in cell-mediated response, binding to and damaging antibody-coated cells or modulate function of B cells acting as helper or suppressor cells, activate macrophages and attract+activate neutrophils. Some have cytotoxic effect without prior recognition of antigen and subset of T-cells also has regulatory function, maintaining immune tolerance.
What are monocytes?
Largest cell present in blood, have lobulated nucleus and plentiful cytoplasm. Mature into macrophages or histiocytes in tissues (reticuloendothelial system) which phagocytose and kill microbes and break down cell debris. Present antigens to lymphocytes. Secrete cytokines enhancing inflammatory response and growth factors, promoting neutrophil and monocyte production. Destroy parasites and red blood cells at end of life, storing haemoglobin to recycle.
What are platelets?
Small particles formed by fragmentation of cytoplasm of megakaryocytes. Function in primary haemostatic response, forming platelet plug at site of small vessel injury. When activated, expose altered phospholipid on surface interacting with coagulation factors to promote blood coagulation at site of tissue injury. Survive for 10 days.
What cells circulate in bloodstream?
In healthy subjects, only platelets and end cells of the myeloid and erythroid lineages are released into bloodstream. In erythrocyte lineage, only reticulocyte and polychromatic erythrocyte are released.
What is a reticulocyte?
Formed from nucleated erythroblast which squeezes through endothelium leaving nucleus behind and still contains ribosomes (stains blue on standard stain due to high RNA content). Carries on synthesising haemoglobin since it has ribosome which mature red cell doesn’t and in 1-3 days loses ribosomes, becoming mature. Remodels to hollowed out disc.
How is differentiation of stem cells and progenitor cells to specific cell lineages controlled? Where are E and T produced?
By cytokines: stem cell factor, erythropoietin (erythrocytes), thrombopoietin (megakaryocytes), G-CSF, and GM-CSF. E produced in kidney in hypoxic conditions, leading to earlier release of reticulocytes from bone marrow. T produced by liver and small amounts by bone marrow, upregulated in cases of infection, inflammation and iron deficiency.
What does thrombopoietin do?
Combines with specific receptor on cell membrane. Enhances survival+expansion of HSCs and promotes differentiation of these cells to megakaryocytes.
Where is G-CSF produced and what does it do?
Produced by fibroblasts, endothelial cells and macrophages. Increases neutrophil production, survival and activity while increasing their release from bone marrow.
Where is GM-CSF produced and what does it do?
Produced by lymphocytes and macrophages. Increases proliferation of progenitor cells, accelerates release and prduction in bone marrow of neutrophils and monocytes plus increases their activity.
How does haemopoeitic marrow change through life?
In adults, it is mainly in skull, sternum, ribs, vertebrae, upper sacrum, pelvis and proximal long bones. Extends more widely in children. However, red marrow can re-expand in adults should there be a need for more blood cells.
What is needed for haemopoiesis?
Iron, Folate, Vitamin B-12. Latter two needed for DNA Synthesis and hence required by rapidly proliferating tissue like bone marrow.
