IMMUNOLOGY

Bios 328a textbook-based study of immunologySpring 2003

http://www.lehigh.edu/~sk08/Courses/Bios328/mainpage.htm

First a review…Adopt as a perspective that:

One B-cell produces one antibody

Make that perspective more exacting:One B-cell produces one idiotype.

Cassettes (V, J, [D],) (aka gene segments) “fuse” (to make an idiotype).

Fusing occurs because RAG recognizes one turn/two turn signals on cassettes.

CDR3 develops through junctional flexibility (trimming) and addition of P & N nucleotides (expanding).

CDR1 and CDR2 (especially) and CDR3 become more varied

because of somatic hypermutation.

First a review… now with images

And, I will use images from a different source.

Remember to be critical of what “interpretative” drawings convey…

First a review… now with images

First a review… still with images

RAG: what does it do? …how does it work?

First a review… still with more images

RAG: what does it do? …how does it work?

…what about P&N nucleotides?

PART IV (some new stuff)• How do immunoglobulins assemble?

• Some immunoglobulins are in the surface membrane of immature B-cells while other immunoglobulins of the same idiotype are secreted by mature B-cells. What’s the difference?

• Similarly, identical variable regions can be shared among different isotypes. How?

• B-cells are diploids with two sets of genetic instructions. How does just one set get expressed?

How do immunoglobulins assemble?

Some immunoglobulins are in the surface membrane of immature B-cells while other immunoglobulins of the same idiotype are secreted by mature B-cells. What’s the difference?

Similarly, identical variable regions can be shared among different isotypes. How?

B-cells are diploids with two sets of genetic instructions. How does just one set get expressed?

The general scheme of B-cell development

• STEM CELL

• pro (genitor) Bcell

• pre Bcell

• Ag-selected ( stimulated)- Bcell

• Ab secreting plasma cell