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.
See attached file for full problem description.