Module 2: Normal Leukocytes (lymphocytes) Flashcards
Leukopoiesis
production of wbc
Where are leukocytes produced
bone marrow (neutrophils, eosinophils, basophil, monocyte, few lymphocytes) lymphatic tissue (lymphocytes, plasma cells)
Leukopoietins
specific “poietin” that causes a cell to transform into a mature form
cytokines with leukopoietin activity (4)
Interleukins 1-19
GM-CSF (granulocyte/monocyte colony stim factor)
G-CSF (granulocyte)
M-CSF (macrophage)
2 major functions of leukocytes
Production of chemical mediators and antibodies result in:
phagocytosis of foreign antigen that is labelled by antibodies
Lysis of foreign and infected body cells by direct killing mechanisms
overall functions of leukocytes (6)
Encounters Recognition Activation Deployment Discrimination Regulation
Function: encounters
encounters between foreign antigens and recognition cells (lymphs and macros)
- continuous flow of circulation through lymph nodes
- large # of lymphs and motile macros circulating in blood/lymph/tissue on patrol for foreign antigens
Function: Recognition
antigen specific receptor molecules on surface of lymphs and production of specific antibody molecules to bind and identify homologous antigens
Function: Activation
lymphs activated when antigen is recognized as foreign
produce antibodies that direct the activities of other cells for immune response
Function: Deployment
lymphs unable to destroy antigen by itself
deploys forces and amplify/distribute their own defences and collaborate with non-antigen-specific phagocytes to destroy antigen
Function: Discrimination
essential to differentiate between self and foreign antigen (avoid autoimmune tissue damage)
Function: Regulation
regulates intensity of immune response so that it has an appropriate antigenic response and shuts off when antigen is eliminated
Lymphocyte responsibilities
detection and recognition of foreign antigen/abnormal self-antigen
initiating specific responses against the antigen
direct cytolytic killing
production of antibodies and lymphokines
Types of lymphocytes (3)
B Lymphocytes
T Lymphocytes
Null Cells (killer cells, natural killer cells)
B lymphocytes
primary source for humeral immune responses (antibody) by transforming into plasma cells
T Lymphocytes
cellular immune responses
involved in regulation of antibody reactions by helping or suppressing the activation of B lymphs
Null Cells
lack B or T cell surface markers
Killer cells: Antibody dependant cell-mediated lysis
Natural Killer cells: Direct cytotoxic activity
How do lymphs differ from other leukocytes (4)
1) resting cells that undergo mitosis into memory/effortor cells when stimulated
2) recirculate back and forth between blood and tissues
3) B and T cell able to rearrange antigen receptor genes to produce different antibodies and surface receptors
4) T and Null cells develop/mature outside of bone marrow
Site of lymphocyte maturation
Embryonic: developed from pluripotent cells of yolk sac and liver
Fetal-adult: stem cells in bone marrow
What influences stem cells into lymphs
IL1 and IL6 turn stem cell into lymphoid stem cell (CFU-L)
then matures into primary and secondary
Primary Lymphoid tissue
do not require antigenic stimulation
Thymus: stem cells multiply under cytokines to become T-lymphs
Bone marrow: stem cells become B-lymphs
Secondary Lymphoid Tissue
Lymph nodes, spleen, mucosal associated lymphoid tissues
Require antigenic stimulation (an active immune response)
Acts as main storage areas of already differentiated lymphs
Lymphoblast characteristics
15-20 um
N:C ratio 4:1
Nucleus: round to oval, 1-2 nucleoli, fine chromatin clumping
Cytoplasm: no granules, medium blue, may have dark blue border
Prolymphocyte characteristics
15-18um
NC ratio 4:1 to 3:1
Nucleus: oval to slightly indented, 0-1 nucleoli, slightly dense chromatin clumping
Cytoplasm: may have granules, med blue with dark rim
Lymphocyte characteristics
6-9um (small) 17-20um (large) NC ratio 4:1 - 3:1 (small) 2:1 (large) Nucleus: round to oval, may have indents, no nucleoli, dense clumped chromatin Cytoplasm: few granules, light blue
Lymphocyte maturation stages
lymphoblast
prolymphocyte
lymphocyte
Lymphocyte maturation summary
nucleus gets denser and smaller
loss of nucleoli
granules may form
cytoplasmic color from dark blue to light blue
Normal lymphocyte values
birth-4: higher than adults
Adults: 20-40% lymphs
of which 60-80% is T cells, 20-35% B cells
Only mature lymphs are found in peripheral blood
B and T cells cannot be distinguished from each other with routine stain
Small Lymph characteristics
Nucleus: round, oval, indented, medium-deep purple, densely clumped, NO NUCLEOLI
Cytoplasm: scant to moderate amount, colourless to royal blue, rarely contains azurophilic granules
Large lymph characteristics
Nucleus: Round, oval, indented, stretched, light-med purple, slightly less clumped, may contain nucleoli
Cytoplasm: moderate to abundant amount, colourless to blue, may contain azurophilic granules in a localized area
Azurophilic granules
non specific granules
Variant Lymphocyte
AKA atypical or reactive lymphs
“working” lymphs
normally 5-6% of lymphs seen in peripheral blood
Represent normal immune system
Increased # in viral disorders
Stimulated lymphs with increased DNA/RNA activity
Characteristics of variant lymphs
increased size
nucleus folded, indented or lobulated
chromatin clumping varies (fine to dense)
nucleoli may be present (often 1-3)
Cytoplasm foamy, vacuolated, usually abundant
may have azurophilic granules
cytoplasm color from greyish to deep blue
