IgG IgD IgEIgAIgM

• Bone marrow gives rise to B cells.

• Mature B cells migrate to lymphoid organs.

• A mature B cells recognizes epitopes.

Clonal Selection

Hallmarks of the

Immune Response

• Self/Non-self Discrimination

• Memory

• Specificity

A. Self/non-self discrimination - One characteristic feature of the specific immune system is that it normally distinguishes between self and non-self and only reacts against non-self.B. Memory - A second feature of the specific immune response is that it demonstrates memory. The immune system "remembers" if it has seen an antigen before and it reacts to secondary exposures to an antigen in a manner different than after a primary exposure. Generally only an exposure to the same antigen will illicit this memory response.C. Specificity - A third characteristic feature of the specific immune system is that there is a high degree of specificity in its reactions. A response to a particular antigen is specific for that antigen or a few closely related antigens

T-independent Antigens

Figure 17.17

B cell

Self-tolerance

• Body doesn't make Ab against self

• Clonal deletion

–The process of destroying B and T cells that react to self antigens

T-Dependent Antigens

Figure 17.16

Clonal Selection

Cellular Events in 1o Response to

T-dependent Ags• Lag

– Clonal selection

• Log– IgM– Class switching

• Stationary

• Decline

• Memory Cell Pool

IgM

Memory Cells

IgG

1o Ag

Cellular Events in 2o Response to

T-dependent Ags• Lag phase– Virgin cells– Memory cells

• Log phase– Pool size– IgG, IgA or IgE

• Stationary

• Decline– Sustained

production

IgM

Memory Cells

IgG

IgG

Memory Cells

Memory Pool

Virgin B cell

Memory T cells

Th

Memory Cells

Th

Th

Memory Cells

Memory Pool

Virgin cell

• T Cells– Virgin cells– Memory cells

• Th cells– Cytokines

• Long Term Memory

Animation of cell selection

TORTORA • FUNKE • CASE

Immunoglobulin Genetics

IgG IgD IgEIgAIgM

How many types of Abs???

•100 Millions

•100,000,000 = 108

Immunoglobulin GeneticsHistory

• Same C region could associate with many V regions– IgG Ab with different specificities

• Same V region could associate with many C regions– Same idiotype on IgG and IgM Ab

• V and C regions coded for by separate genes

Light Chain Gene FamiliesGerm line gene organization

J1 C1

E

J2 C2

E

J3 C3

E

J4 C4

EP

L V1

P

L Vn

P

L V2

Lambda light chain genes; n=30

P

L V 1

P

L V n

P

L V 2 J2 J3 J5 C

E

J1 J4

Kappa light chain genes; n=300

Light Chain Gene FamiliesGene rearrangement and expression

L V 1 L V nL V 2 J2 J3 J5 CJ1 J4

DNAP PP E

P P E

L V 1 L J5 C

V 2 J4

DNA

DNA Rearrangement

V CJ

V C

Protein

Transport to ER

Protein

TranslationCL V J

E

L V CJ

RNA

Transcription

Primary transcript

CL V JRNA Processing

RNAmRNA