Studies on T Lymphocytes and Mammalian Memory 
devoid of a large number of TL class I genes. Also 
being pursued is biochemical characterization of 
a TL class I molecule encoded by the gene 73'', 
whose product has been shown to be expressed 
specifically on the surface of gut epithelial cells 
with which a 76 T cell subset, i-IEL, is associated. 
We intend to purify the putative peptides bound 
to the T3^ molecule and subject them to microse- 
quencing. The sequences may lead to the identi- 
fication of the antigenic proteins. 
We have pursued functions of 76 T cells by im- 
munizing KN6 transgenic mice with the ligand- 
bearing C57BL/6J spleen cells and following the 
proliferation of the transgenic cells and the disap- 
pearance of the injected spleen cells from the 
host spleen. These studies indicate that KN6 76 T 
cells are capable of responding to the allogenic 
cells by cytotoxicity. 
Functions of 76 T cells have also been studied 
by following the antibody response of afi T-defi- 
cient mutant mice to thymus-dependent and 
-independent antigens. So far these mice respond 
only to the thymus-independent antigen. A possi- 
ble role of 76 T cells in this type of antibody re- 
sponse is being studied using 76 T-deficient mu- 
tant mice. The T- or 76 T-deficient mice have 
also been infected with listeria, mycobacteria, or 
malaria. Resistance and/or immunity against 
these infectious agents will be determined. We 
are also studying the response of the mutant mice 
to skin grafts and injected tumor cells. 
In addition to the studies on 76 T cells, we 
found, using the multigene transfection tech- 
nique, that the afi TCR-CD3 complex can be ex- 
pressed on the surface of nonlymphoid cells 
without either the CD37 or CD35 subunit. This 
suggests the intriguing possibility that these mul- 
tiple forms of TCR-CD3 complex are utilized by 
normal T cells for difi'erential purposes. The hy- 
pothesis is being tested by producing mouse mu- 
tants that are defective either in the CD37 or 
CD36 gene. 
We are also interested in studying how infor- 
mation is stored and retrieved in the brain. The 
approach that we have taken is to investigate the 
biochemistry, physiology, and behavior of mice 
mutant for genes thought to be involved in synap- 
tic plasticity. Using homologous recombination, 
we have disrupted the a-subunit of the calcium 
calmodulin kinase II (CaMKII) gene in embry- 
onic stem cells and have used these cells to gener- 
ate a mouse strain lacking the gene. The a-sub- 
unit of CaMKII is neural specific and comprises 
most of the CaMKII holoenzyme in postnatal hip- 
pocampus and forebrain. Peptides that emulate 
either the calmodulin-binding domain or the in- 
hibitory domain of this kinase seem to block the 
induction of long-term potentiation (LTP) . Mice 
lacking the a-subunit develop normally and are 
viable. 
Gross neuroanatomical studies did not detect 
any abnormalities. We studied the electrophysiol- 
ogy of the CAl fields of the mutant hippocampus 
in collaboration with the laboratory of Charles 
Stevens (HHMI, Salk Institute). In normal animals 
we were able to induce LTP in more than 90 per- 
cent (n = 12; 3 animals) of all slices. However, 
we could stably potentiate less than 1 0 percent of 
slices from mutant animals (« = 17; 5 animals). 
Furthermore, the unpotentiated excitatory post- 
synaptic potentials of normal and mutant animals 
were identical, suggesting that synaptic transmis- 
sion was not impaired in the mutant animals. 
We also studied the mutant mice in difl'erent 
versions of the Morris water maze, in collabora- 
tion with Jeanne Wehner's laboratory. The results 
indicate that the mutant mice, but not their nor- 
mal litter mates, are specifically impaired in tasks 
that demand the use of configured spatial infor- 
mation. Our analysis of the mice mutant for the a 
CaMKII demonstrates the involvement of this ki- 
nase with LTP and with configural learning. 
Past evaluations of the involvement of LTP on 
learning and memory have mainly depended on 
the potential role that the NMDA (7V-methyl-D- 
aspartate) receptor plays on both phenomena. Un- 
fortunately, NMDA blockers seem to impair both 
learning and performance, confounding the in- 
terpretation of those experiments. However, our 
results suggest that performance measures unre- 
lated to learning were not responsible for the 
learning impairment observed in our mutant 
animals. 
A key aspect of our studies has been the appar- 
ent specificity of the phenotype: the develop- 
ment and neuroanatomy of the mutant mice are 
apparently normal, as well as nonpotentiated syn- 
aptic transmission. Furthermore, behavioral anal- 
ysis of the mutant animals argues for a selective 
impairment on hippocampal-dependent learn- 
ing. We are continuing to test the Hebbian hy- 
pothesis by making mutants for other compo- 
nents of LTP and for genes that might affect 
the physiology of specific regions involved in 
learning. 
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