Discussion:
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
|
-
|
-
|
-
|
-
|
|