Lecture 1 - Intro to Immunology Flashcards
Blood smear (types and importance)
Types:
1) complete blood count (CBC) 2) Differential Leukocyte count (DIFF)
Together, both provide a complete hematological profile of a case in terms of structure and morphology —– diagnostic clues of a disease
How to make a blood smear
1) One end thick, other thin
2) Zone of morphology (area of optimal thickness for light microscope) is 2cm in length
Giemsa Stain
-Stain of basic stain “methylene blue” and acidic stain “eosin”, which allows you to see and differentiate different types of leukocytes
WBC components and percentage
- Neutrophils: 40-70
- Eosinophils: 1-4
- Basophils: 0.5-1
- Monocytes: 2-8
- Lymphocytes: 20-40
Cluster of Differentiation
- CDs. - surface cell markers
- Allows one to differentiate B, T and NK cells under a microscope where specific antigens (CDs) are identified on the cell and selectively expressed
-Direct and Indirect fluorescence Microscopy is used
Leukocytes cell markers for CDs (and nomenclature)
Tcell - CD3, CD4, CD8
Bcell - CD19, CD20
NKcell - CD56
Macrophage/monocyte - CD14
-If Ag for CD4 is present on a Tcell, it would be “CD4+T-cells” and if expression is high, a “hi” would follow the name
Phagocytes
-Neutrophils and monocytes (blood) and macrophages (tissue — but from monocytes)
Functions:
1) Ingest and destroy microbes, then get rid of damaged tissues
2) Secrete cytokines for immune regulation
Scavenger function
Phagocytes tendency to get rid of damaged microbe tissue
Phagocyte functional response
1) Recruitment - of cell to infection site
2) Recognition – of microbes
3) Ingestion – via phagocytosis
4) Destruction – of microbes
Neutrophils
- Nucleus with 3-5 lobules
- highest abundance circulating WBC
- Mediate early inflammation via cytokine, etc. release
- Contain cytoplasmic granules
- apoptosis after hours or days
Cytoplasmic granules
- In NK and cytotoxic T cells
- Contain peroxidase, lysozyme, degradative enzymes, defensins
Leukocytosis
- WBC count above 11k cell/mcL
- Neutrophilia is most common type but can also be due to basophils, eosinophils, etc
-Sign of infection, 2-3 fold increase in circulating WBC during inflammation
Causes of Leukocytosis
Mild
- inflammation - necrosis - stress - drugs - pregnancy
Red flags (for malignant cause)
- unwell person
- severe neutrophilia
- left shift
Left shift
Greater than 5% circulating immature neutrophils — bone marrow releasing more immature WBC due to need
Leukopenia
- WBC count less thank 4k cells/mcL
- Neutrophenia
Neutropenia
- aka Agranulocytosis/Granulocytopenia
- reduction in circulating neutrophils
- increased risk of infection
- often caused by radiation therapy
Neutrophil Killing Mechanisms
- Intra or extracellular
1) Phagocytosis - engulfed, killed by digestive enzymes
2) Degranulation - enzymes released from granules, killed extracellularly (bow and arrow)
3) NETs
NETs
- Neutrophil extracellular traps
- Released by neutrophils to kill microbes
- Contain DNA, histones, proteins, enzymes
- Paralyze pathogen and facilitate phagocytosis
KEY: Neutrophils continue activities after NET formation
Monocytes
- Primary mononuclear phagocytes in blood (macrophages in tissue)
- From bone marrow, M-CSF
- 3-8% WBC in blood
- Can live few days or much longer if needed for inflammation
Dendritic cells
- Similar to macrophages in function –> capture and process antigens
- Best of APC (antigen presenting cells)