Blood And Bone Marrow Response To Infection

Question 1

What are some characteristic features of a lymphocyte under a gram stain?

Answer 1

• blue cytoplasm
• clumped chromatin
• typically without granules

Question 2

What are some common features of a virus infection in a blood film? Name some examples of viral infections.

Answer 2

Thrombocytopenia - low platelet count
Reactive T cells - increased size, basophilic cytoplasm

Examples of viral infection: Epstein-Barr Virus EBV, cytomegalovirus CMV, varicella, Viral Hepatitis, Dengue fever, Parvovirus

Question 3

Outline the process of EBV driven lymphoma formation

Answer 3

EBV proliferates in B cells and then turns off its antigens to evade the immune response. In immunocompromised hosts, the virus selects abnormal B cells which proliferate to form a lymphoma

Question 4

What are some of the features of Bordetella pertussis infection on a gram stain? What’s the common name for the infection?

Answer 4

Lymphocytosis - increased lymphocytes due to a lymphocyte promoting factor secreted by the bacteria that inhibits lymphocyte migration to the tissues
Leucocytosis - lots of WBC’s, indicates infection

Common name is Whooping Cough

Question 5

What is haemophagocytosis? How does it alter blood cells (in terms of their count)? What infections is it associated with?

Answer 5

Macrophages phagocytose haemopoietic cells in the bone marrow

Causes pancytopenia - cytopenia all multiple cell types (leucopenia, anaemia, thrombocytopenia)

Associated with any infections - viral (EBV, CMV, varicella), bacterial, fungal, protozoal

Question 6

Name 3 characteristics of parvovirus in a gram stain.

Answer 6

Anaemia - caused by reduced erythropoiesis
Giant erythroblasts with viral inclusions
Reticulocytopenia

Question 7

On a gram stain, what features would indicate bacterial infection?

Answer 7

Neutrophilia - increased neutrophils (note: neutropenia is seen in sepsis)
Left shift - increased immature/precursor cells
Toxic granulation - neutrophils contain more granules
Dohle bodies - remnants of ER in the cytoplasm of neutrophils (look like blue inclusions)
Vacuolation- increased vacuoles in neutrophil cytoplasm
Rouleaux- stacking of rbc caused by increased immunoglobulins
Thrombocytopenia - low platelet count
Hypercellular bone marrow - ready to release lots of precursors
Granulomas in the bone marrow