Leukocytes Flashcards
Leukocytes function
are mobile cells, Highly motile, use amoeboid movement, attracted via chemotaxis, function as active part of immune system in tissues
how do mobile cells leave circulation?
margination, pavementing, and diapedesis
pavementing
rolling and adhesion
diapedesis
extravasation
pseudopodia
WBC’s stick to endothelial cell surface, squeeze between endothelial cells of capillaries & venules
chemotaxis
how WBC attract to inflammatory sites via cytokines, which are any cell product that influences another cell like pheromone
how are WBC categorized
granulocytes
agranulocytes
All WBC possess what?
1’ granules, which contain lysosomal enzymes (ex. acid hydrolases)
what color do azurophilic granules stain
stain blue-purple
What do granulocytes possess?
specific granules, 2’ granules
2’ granules
- absent in agranulocytes
- contain lysozyme& alkaline phosphatases
- Exhibit variable staining
types of granulocytes
- basophils, eosinophils, neutrophils
- All have single, multi-lobed nucleus & prominent cytoplasmic granules
Neutrophils
- Most common, Multi-lobed nucleus (3-5 lobes) = polymorphonuclear cells (PMN’s)
- Short-lived; tissue lifespan several hrs—days
- Few mitochondria—use 1’ anaerobic glycolysis
myeloperoxidase
1’ granules of neutrophils also contain unique antimicrobial
what do 2’ granules stain?
basophilic or eosinophilic, (“neutral”)
what do neutrophils contain?
Contain inflammatory mediators & complement activators; proteases, defensins, lactoferrin, & lysozyme (antibacterial compounds)
degranulation
- how neutrophils release during inflammatory rxn
- Release of granule contents into ECS
Neutrophils possess small 3’ granules, which contain what?
gelatinase, which breaks down collagen
Neutrophils are assoicated with acute inflammation
generally last several days
Cardinal signs of inflammation (4)
Rubor, tumor, calore, et dolore (redness, swelling, heat & pain)
what are neutrophils attracted to?
Attracted to bacteria & damaged tissue by chemotactic factors
What does the function 1’ in phagocytosis lead to?
formation of phagolysosome to digest bacteria
how are phagocytosis enhanced?
via opsonization—coating of bacteria with Ab & complement to enhance phagocytosis
respiratory burst
bacterial killing by generating hydrogen peroxide & hypochlorous acid
“Stab” cells
=bandcells—immature neutrophils
Barr body
inactive X chromosome in females
Basophils
- Least common of WBC’s
- Bilobed nucleus
- May or may not be circulating equivalent of mast cells in tissue
- Characterized by large, basophilic specific granules
is mast cell lifespan uncertain?
yes
In basophils, what do specific granules contain?
- Hydrolytic enzymes,
- Heparin sulfate
- Chondroitin sulfate
- Histamine
- Leukotrienes
heparin sulfate
an anticoagulant
chondroitin sulfate
proteoglycan
Histamine
vasoactive amine => vasodilation & ↑vascular permeability
Leukotrienes
slow reacting substance of anaphylaxis(SRS) => smooth Mm contraction (asthma) eosinophilic chemotactic factor (ECF)
what uses type I (immediate) hypersensitivity rxn’s
Basophils; seen in asthma, hayfever, & some types of allergic dermatitis
If hypersensitivity rxn is severe, what occurs in basophils?
anaphylaxis (very rapid, severe immune rxn)
what counteract effects of basophils?
eosinophils
Eosinophils
- Bilobed nucleus
- Remain in circulation before entering tissue
- Tissue lifespan 8-12 days
- Have surface receptors for IgE
- Large eosinophilic specific granules contain hydrolytic enzymes
Large eosinophilic specific granules contain hydrolytic enzymes?? (4)
- histaminase: neutralizes histamine
- eosinophil peroxidase(EPO): special peroxidase
- Lysosomal enzymes
Major basic protein (neutralizes heparin, kills parasites)
what are eosinophils chemotactically attracted to?
basophils and mast cells via ECF (eosinophilic chemotactic factor)
Ameliorate & counteract hypersensitivity rxn’s & effects of histamine:
Release eosinophil derived inhibitor (inhibits basophil & mast cell degranulation)
Eosinophils Function
- antiparasitic function, especially against flukes (helminths) & affinity for Ag-Ab complexes
- Parasites & Ag-Ab complexes destroyed by major basic protein & subsequent phagocytosis
2 types of agranulocytes
monocytes & lymphocytes
agranulocytes
single, unlobed nucleus, lack 2’ (specific) granules, but have 1’ azurophilic granules
Monocytes
- Largest WBC
- Abundant, gray-blue/lavender cytoplasm; large indented (“kidney bean” shaped) nucleus
- Lifespan in tissue several months
What happens to monocytes when they enter tissue?
Present in bloodstream 2-3 days, then extravasate, enter tissue, become macrophages (= histiocytes)
when monocytes turn into macrophages, they remained fixed in the same tissue. What are the fixed tissue locations?
- Kupfer cells in liver
- microglial cells in CNS
- Langerhans cells in skin
- dust cells in lung
- osteoclasts in bone
Macrophages
- highly mobile, phagocytic—contain abundant hydrolytic enzymes
- Active in subacute to chronic infections, along with lymphocytes
- Can fuse together to become (multinucleate) epithelioid giant cells in chronic granulomas
- function as Ag-presenting cells in lymphoid organs
Lymphocytes
- Active in subacute to chronic infections
- Have lifespan of days to years
- Two size classes—small and large lymphocytes
- Size classes do not correlate with cell types
- Characterized by round, densely staining nucleus surrounded by thin rim of cytoplasm
- 1’ cell of immune system—recirculating, immunocompetent cells
what are 2 major types of lymphocytes?
b-cells (~4-10 %) & t-cells (~90 %)
B cells
- First recognized in Bursa of Fabricius of birds
- In mammals, formed in bone marrow & become immunocompetent there
- Function: in humorally mediated immmune response—produce Ab’s
- Function: in anamnestic response of humoral immunity;Premise of vaccination to prevent disease
- Ag-presenting cells
what happens to B cells after encountering Ag?
undergo multiple divisions to produce clone of Ab-producing plasma cells; Called amplification, or clonal expansion
what happens to B and T cells if they do not replicate?
remain as long-lived memory cells or effector cells
what surface markers and immunoglobulins are on B cells
HLA Type I
HLA = human leukocyte Ag—major histocompatability complex [MHC] molecules
T cells
- “Thymus-dependent” lymphocytes
- Formed in bone marrow, but migrate to thymus to become immunocompetent
- Responsible for cell-mediated immunity; have long lifespan
- “cluster of differentiation” determinant molecules (CD molecules) on surface—->Recognize HLA receptors on surface of other cells (prevent “self”-destruction)
Paratopes
T-cells have receptors on cell surface like those present on Ab’s. Recognize foreign proteins of Ag’s (epitopes)
Types of T cells (3)
- Cytotoxic
- suppressor
- helper lymphocytes
Cytotoxic, or killert-cells (Tc/Tk)
- 1’ effectors in cell-mediated immunity—tend to be large lymphocytes
- Recognize cells with foreign surface Ag’s or receptors & kill them
- Punch holes in plasma membranes
Helper t-cells (Th)
- Detect invaders, sound chemical alarm
- Recognize Ag, usually presented by Macrophage or b-cell, then secrete lymphokines (cytokines)—act as pheromones, stimulate b-cells => Ab production, or Tk cells => kill
Suppressorcells (Ts)
•Suppress activity of b-cells, dampen immune response, especially to “self” molecules
Autoimmune diseases
loss of control of Ts cells
Null cells
-Lymphocytes which possess Fc receptors but lack specific cell surface markers of either b-or t-cells (null)
-include natural killer cells
possibly some pleuripotential stem cells
Null cells function
- Responsible for nonspecific cytotoxicity against virus-infected & tumor cells
- Also function in Ab-dependent, cell-mediated cytotoxicity (ADCC)
Complete blood count (CBC)
total # of WBC’s
differential cell count
relative % of WBCs
↑WBC’s
infection/ tumor
philia (neutrophilia), -osis (mononucleosis)
↑neutrophils—acute, bacteria
↑lymphocytes (& monocytes)—subacute, viral
↑ eosinophils—allergies, parasites
↓in WBC’s
immune suppression/ tumor
ex. -penia
-penia
- neutropenia—acute viral infection or severe sepsis
* thrombocytopenia—↓ platelets
