B LYMPHOCYTE TO SURFACE MARKERS

b lymphocyte

• represents 20-35% of lymphocyte population

• matures at bone marrow

• precursor cells in the antibody production

• these are the precursor of plasma cells

pro b cells (progenitors)

• has distinctive markers that include surface antigens cd19, cd45r, cd43, cd24, and c-kit

• intracellular proteins found at this stage are tdt, and recombination-activating genes rag1 and rag 2, which code for enzymes involved in gene rearrangement

• ckit on this stage interacts with a cell surface molecule called stem cell factor, which is found on stromal cells

• rearrangement of genes on chromosome 14, which code for the heavy chain part of the anitbody

pre-b cells (precursors)

• when synthesis of the heavy chain part of the antibody molecule occurs, this stage begins

• the first heavy chains synthesized are the u chain, which belong to the class of immunoglobulins called igm

• these u chains accumulate in the cytoplasm

• may also express u chain on the cell surface, accompanied by an unusual light chain molecule called surrogate light chain

immature b cells

• are distinguished by the appearance of complete igm molecules on the cell surface

• this indicates that rearrangement of the genetic sequence coding for light chains on either chromosome 2 or 22 has taken place by this time

• other surface proteins that appear on the immature b cell include cd21, cd40, and mhc class 2 molecules

mature b cells

• in the spleen, immature b cells develop into this stage known as either marginal zone b cells or follicular b cells

marginal b cells

• remain in the spleen in order to respond quickly to any blood-borne pathogens the may come into contact with

follicular b cells

• migrate to lymph nodes and other secondary organs

• unlike marginal b cells that remain in the spleen, this constantly recirculating throughout the secondary lymphoid organs

• this exhibits igd, another class of antibody molecule, on their surface

activated b cells

• antigen-dependent activation of b cells takes place in the primary follicles of peripheral lymphoid tissue

• exhibit identifying markers that include cd25, which is found on both activated t and b cells and acts as a receptor for interleukin 2

• they transform into blasts that will give rise to both plasma cells and so called memory cells

plasma cells

• are spherical or ellipsoidal cells between 10 and 20 um in size and are characterized by the present of abundant cytoplasmic immunoglobulin and little to no surface immunoglobulin

• this represents the most fully differentiated lymphocyte, and its main function is antibody production

• are not normally found in the blood but are located in germinal centers in the peripheral lymphoid organs

granzymes

• are a class of enzymes called serine proteases

• once they are in the cytoplasm of the target cell, a cascade of events is initiated that fragment the target cell dna into small pieces

• do not directly break down dna, but they activate a nuclease that destroys the target cell dna as well as any viral dna that may be contained inside it

• can also activate enzymes in the target cells that disrupts the cell’s mitochondria

perforin

• are pore-forming proteins that polymerize in the presence of calcium and form channels in the target cell membrane

memory b/t cells

• are populations of long-lived t or b cells that have been stimulated by antigen

• they can make a quick response to a previously encountered antigen

• carry surface igg as their antigen receptor; express the cd45ro variant of the leukocyte common antigen and increased levels of cell adhesion molecules, chemical mediators involved in inflammatory processes throughout the body

t cells

• develop in the thymus

• found in the blood (60-80%), thoracic duct fluid, lymph nodes

• identified by rosette formation with srbc

• end products of activation are cytokines

• antigen includes: cd2, cd3, cd4, cd8

• located in the paracortical region of lymph nodes

b cells

• develop in the bone marrow

• found in bone marrow, spleen, lymph nodes

• identified by surface immunoglobulin

• end products activation is antibody

• antigens include: cd19, cd 20, cd21, cd40, mhc class 2

• located in cortical region of lymph nodes

cd 2

• thymocytes, t cells, nk cells

• involved in t cell activation

cd 3

• thymocytes, t cells

• associated with t cell antigen receptor; role in tcr transduction

cd 4

• helper t cells, monocytes and macrophages

• co-receptor for mhc class 2; receptor for hiv

cd 5

• mature t cells, thymocytes, subset of b cells

• posiitve or negative modulation of t and b cell receptor signaling

cd 8

• thymocyte subsets, cytotoxic t cells

• co receptor for mhc class 1

cd 10

• b and t cell precursors, bone marrow stromal cells

• protease; marker for pre-b, calla

cd 16

• macrophages, nk cells, neutrophils

• low affinity fc receptor, mediates phagocytosis and adcc

cd 19

• b cells, follicular dendritic cells

• part of b cell co receptor; signal transduction molecule that regulates b cell development and activation

cd 21

• b cells, follicular dendritic cells, subset of immature thymocytes

• receptor for complement component c3d; part of b cell co-receptor with cd 19

cd 23

• b cells, monocytes, follicular dendritic cells

• regulation of ige synthesis; triggers release of gm csf from monocytes

cd 25

• activated t, b cells, monocytes

• receptor for il2

cd 44

• most leukocytes

• adhesion molecule mediating homing to peripheral lymphoid organs

cd 45r

• different forms on al hematopoietic cells

• essential in t and b cell antigen-stimulated activation

cd 56

• nk cells, subsets of t cells

• not known

cd 94

• nk cells, subsets of t cell

• subunit of nkg2-a complex involved of nk cell cytotoxicity