Spleen, White Cells, Cytopenia Flashcards
Distinguish between red and white pulp in spleen
- Red pulp - sinuses lined by endothelial macrophages and cords
- Removes old red cells and metabolises haemoglobin
- White pulp - similar structure to lymphoid follicles
- Synthesises antibodies and removes antibody-coated bacteria and blood cells
Explain how blood enters the spleen
- Blood enters via the splenic artery
- White cells and plasma preferentially pass through the white pulp
- Red cells preferentially pass through the red pulp
What are the functions of the spleen
- Sequestration and phagocytosis - old/abnormal red cells removed by macrophages
- Blood pooling - platelets and red cells mobilised during bleeding
- Extramedullary haemopoiesis - pluripotent stem cells proliferate if bone marrow fails or during haematological stress
- Immunological function - check for pathogens in blood
What are the causes of splenomegaly
- Back pressure - portal hypertension in liver disease
- Overworking red pulp - removing red cells
- Overworking white pulp - synthesising antibodies
- Reverting to what it used to do - extramedullary haemopoiesis
- Infiltration of cells - leukaemia, lymphomas
- Chronic lymphocytic leukaemia - expanded white pulp and infiltration of lymphocyte
- Accumulation of waste products of metabolism
- Gaucher’s disease
- Infiltrated by other material - sarcoidosis
- Infiltration of granulomas
How is splenomegaly seen on a scan
Attenuation (spots) seen and grown irregularly
What is hypersplenism and its effects
- Overactive spleen
- Pooling of blood in enlarged spleen - destroy blood cells due to pancytopenia or thrombocytopenia
- Risk of rupture if enlarged and no longer protected by rib cage
- Haematoma (blood clotting) around enlarged spleen after rupture - could cause anaemia or hypertension
What is hyposplenism and its risk
- Lack of functioning splenic tissue
- Associated with increased risk of sepsis
What are the causes of hyposplenism
- Splenectomy
- Sickle cell disease in older children and adults (due to multiple infarcts then fibrosis)
- Coeliac disease (inflammation of small intestine)
Explain the blood film in hyposplenism
- Howell jolly bodies (DNA remnants)
- Basophilic clusters of DNA in circulating erythrocytes
- During erythropoiesis, erythroplasts normally expel their nuclei but in some cases a small portion of DNA remains
- Normally removed in spleen
Define cytopenia
Reduction in number of blood cells
What colour do basophils, neutrophils and eosinophils stain in H&E stain
- Basophils - dark blue
- Neutrophils - neutral pink
- Eosinophils - bright red
How can neutrophils be identified on a blood film
Polymorph - multilobed nucleus
What is the role of G-CSF glycoprotein
- Neutrophils maturation controlled by a hormone G-CSF
- Increase production of neutrophils
- Decrease time to release mature cells from bone marrow
- Enhances chemotaxis
- Enhances phagocytosis and killing of pathogens
- Can be administered for patients who need neutrophils
How is neutrophilia caused
- Occurs in infection, tissue damage, acute inflammation, acute haemorrhage, cancer
- Minor increases by drugs, cytokines (G-CSF), metabolic/endocrine disorders, smoking
- Myeloproliferative disorders - increase production of blood cells in bone marrow
What are the causes of neutropenia
- Due to reduced production or increased removal/use
- Increased removal/use caused by immune destruction, sepsis, splenic pooling
- Reduced production due to B12/folate deficiency
- Infiltration of bone marrow by malignancy or fibrosis
- Aplastic anaemia (empty marrow)
- Radiation
- Drugs
- Viral infection - very common
- Congenital disorders
What are the consequences of neutropenia
- Susceptible to severe bacterial and fungal infection
- Mucosal ulcerations eg. Painful mouth ulcers
What is the medical term for high/low RBC, white cell, neutrophil, platelet, lymphocytes and low red + white cell + platelet
- RBC - anaemia, erythrocytosis
- White cell - leucopenia, leucocytosis
- Neutrophil - neutropenia, neutrophilia
- Platelet - thrombocytopenia, thrombocytosis
- Lymphocytes - lymphocytopenia, lymphocytosis
- Red + white + platelet - pancytopenia
Explain monocytes and their role
- Response to inflammation and antigenic stimuli
- Circulate in blood for 1-3 days before moving into tissues and differentiating into macrophages or dendritic cells
- Half are stored in red pulp in spleen
- Monocytes, macrophages and dendritic cells - phagocytosis, antigen presentation, cytokine production
When does monocytosis occur
Chronic inflammatory conditions
What does eosinophils look like on a blood film
Bi-lobed nucleus
What is the role of eosinophils
- Responsible for dealing with parasites
- Mediator for allergic reactions eg. Asthma
- Migrate to epithelial surfaces
- Release granular content containing enzymes aids in destruction and subsequent phagocytosis of pathogens
What are the causes of eosinophilia
- Allergic diseases - asthma, eczema, hay fever
- Drug hypersensitivity - penicillin
- Churg-Strauss - blood vessel inflammation
- Parasitic infection - roundworm, tapeworm, flukes, helminths
- Skin diseases
- Lymphoma, leukaemia, myeloproliferative conditions
How do basophils look on a blood film
Contain large cytoplasmic granules which may obscure cell nucleus when stained
What is the role of basophils
- Active in allergic reactions and parasitic infections
- Dense granules contain histamine, heparin, hyaluronic acid, serotonin
- Released following binding of IgE to surface receptors
What are the causes of basophilia
- Hypersensitivity to drugs
- Infections - chicken pox, influenza, tuberculosis
- Myeloproliferative - leukaemia, thrombocythemia
Describe the role of lymphocytes
- Natural killer cells - cell-mediated cytotoxic innate immunity
- T cells - facilitate cell-mediated adaptive immunity
- B cells - facilitate humoral, antibody-driven adaptive immunity
- Mainly found in the lymph
What are the causes of lymphocytosis
- Viral infections, bacterial infections
- Stress related
- Post splenectomy
- Smoking
- Lymphoproliferative malignancies - chronic lymphocytic leukaemias, T or NK-cell leukaemia, lymphoma - cells ‘spill’ out of infiltrated bone marrow
What are the causes of pancytopenia
- Increased removal due to immune destruction, splenic pooling (hypersplenism) or rarely haemophagocytosis (chewing up of cells in bone marrow)
- Reduced production due to B12/folate deficiency, bone marrow infiltration by malignancy, marrow fibrosis, radiation, viruses, congenital bone marrow failure
