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The Magic
of
Lymphocytes
Cells that take the form of lymphocytes
T cells
cytotoxic
helper cells
suppressor cells
B cells
NK (natural killer) cells
Stem cells
Possible others
pro-mast cells ??
pro-dendritic cells ??
Maturation of B and T Cells
small
lymphocyte
lymphoblast
(prolymphocyte)
Small Lymphocytes can Switch back
and forth into Lymphoblasts
T.
SL = small lymphocyte
Blast = lymphoblast
An Antibody Molecule
An antibody binds to an antigen
Antibody Genes are Cut and Spliced
mRNA transcript
Remove introns
The exact position of gene
splicing is variable.
End of a v segment
Beginning of a d segment
|G.G.A|C.A.T. ……… T.C.G|T.C.C|G.G.G
variable splicing
|G.G.A|C.A.G ----------- |T.C.C|G.G.G
|G.G.A|C.A. ----------- G|T.C.C|G.G.G
|G.G.A|C. ----------- C.G|T.C.C|G.G.G
|G.G.A|C.A.G------- T.C.G|T.C.C|G.G.G
|G.G.A|------------------ T.C.C|G.G.G
Lymphocytes insert extra nucleotides
into their DNA at junction sites in a
non-templated manner.
|G.G.A|C.A.T. …………… T.C.G|T.C.C|G.G.G
|G.G.A|C.A.T|N.N.N|N.N.N|T.C.G|T.C.C|G.G.G
The Clonal Selection
Theory
Proposes a two stage process
for antibody formation.
B stem cell
Proliferation
Pre B cells
Diversification
B cells
Antigen
stimulation
o
o
o
o
o
o
o
o
o
o
B cell  Lymphoblast
o
o
o
Activated B lymphoblast
o oo
o o
o
o o o
Proliferation
Differentiation
Plasma cells
Antibodies
B memory
cells
B stem cell
Proliferation
Pre B cells
Diversification
B cells
Antigen
stimulation
o
o
o
o
o
o
o
o
o
o
B cell  Lymphoblast
o
o
o
Plasma Cells
T cells
The T cell Receptor
- is homologous to antibody.
- forms by gene rearrangement.
- varies from one T cell to another.
but it
- is always membrane-bound.
- binds to peptides fragments of antigens
These must be held on a cell
surface by an MHC protein.
Cells that take the form of lymphocytes
T cells
cytotoxic
helper cells
suppressor cells
B cells
NK (natural killer) cells
Stem cells
Possible others
pro-mast cells ??
pro-dendritic cells ??
Activation of a T cell by an
Antigen Presenting Cell
Some Inerleukins
Enuff