The Magic of

Lymphocytes

Cells that take the form of lymphocytes

T cells cytotoxic helper cells suppressor cellsB cellsNK (natural killer) cellsStem cellsPossible others pro-mast cells ?? pro-dendritic cells ??

Maturation of B and T Cells

small lymphoblast lymphocyte

(prolymphocyte)

Small Lymphocytes can Switch back and forth into Lymphoblasts

SL = small lymphocyteBlast = lymphoblast

T.

An Antibody Molecule

An antibody binds to an antigen

Antibody Genes are Cut and Spliced

mRNA transcriptRemove introns

The exact position of gene splicing is variable.

|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

End of a v segment Beginning of a d segment

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 processfor antibody formation.

B stem cell

Proliferation Pre B cells

Diversification B cells

Antigen stimulation

B cell Lymphoblast

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Activated B lymphoblast

Proliferation

Differentiation

Antibodies

Plasma cells

B memory cells

B stem cell

Proliferation Pre B cells

Diversification B cells

Antigen stimulation

B cell Lymphoblast

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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 cellsB cellsNK (natural killer) cellsStem cellsPossible others pro-mast cells ?? pro-dendritic cells ??

Activation of a T cell by an Antigen Presenting Cell

Some Inerleukins

Enuff