Immunology

1. A researcher purified mu heavy chains from two inbred* strains,
called C3H and A/J. She immunized mice from each strain with the
other’s mu chains, yielding C3H anti-A/J mu and A/J anti-C3H mu. She
tested each antiserum against normal serum immunoglobulins from the
sources shown:

  Precipitate with serum from:

Antiserum C3H A/J (C3H X A/J)F1

C3H anti-A/J mu - + +

A/J anti-C3H mu. + - +

 

She next attached fluorescein to the C3H anti-A/J mu, and rhodamine to
the A/J anti-C3H mu. These compounds fluoresce (glow) under UV light:
fluorescein glows green and rhodamine glows red. She added these
reagents to B-cells from each strain and from F1's, waited awhile,
washed away the anti-mu reagents. Finally, she looked at the cells under
a special microscope that shines UV light on the sample, so that if one,
the other, or both reagents bound to a cell, it will glow either red,
green, or red and green. The proportion of B cells in each sample
falling into each such category are shown:

  Proportion of B cells in each category from:

cell that glow: C3H A/J (C3H X A/J)F1

green only 0% 100% 50%

red only 100 0 50

red and green 0 0 0

 

From the first table, what do you conclude about mouse m genes and their
expression?

 

From the second table, what do you further conclude?

 

* "inbred" means that these mice have been backcrossed (child x parent
or brother x sister) more than 20 times so that within a given "strain,"
there is homozygosity at all loci.

 

 

2. You have two IgA antibodies made by mouse myeloma cells: One called
M315 that binds DNP; and one called T15 that binds PC. [The PC hapten is
structurally different from DNP]. You synthesized a peptide of three
lysines with DNP on one end and PC on the other: DNP-lys-lys-lys-PC. You
set up nine tubes containing this compound, then added different
combinations of the whole antibodies at 1 mM or their Fab fragments at
10mM.

Notice that the last column has been left blank - that's your job: In
your journal, list the tube numbers, and next to each tube number write
a "yes" if a precipitate would be observed and "no" if it would not.
Explain your reasoning.

 

Tube

# whole

M315 whole

T15 Fab of

M315 Fab of

T15 precipitate

observed?

1 + - - -  

2 - + - -  

3 - - + -  

4 - - - +  

5 + + - -  

6 - - + +  

7 + + + -  

8 + + - +  

9 - - - -