patibility complex (MHC) class I molecules. The 
avian data also suggest that TCRl cells are not sub- 
jected to the intrathymic selection pressures that 
mold the TCR2 cell repertoire. Failure to eliminate 
potentially autoreactive TCRl clones in the thymus 
may suggest an immunoregulatory role for this sub- 
population of T cells. 
A remarkable finding is the generation of a third 
sublineage of avian T cells that develops after the 
TCRl and TCR2 cells. The TCR3 receptors resem- 
ble TCR2, but one of the two receptor chains is 
smaller and has a distinct peptide composition. A 
monoclonal antibody against TCR3 fails to recog- 
nize TCRl and TCR2, and vice versa. Intrathymic 
development of TCR3 cells parallels that of TCR2 
cells, in that surface receptor expression increases 
gradually during the maturation process, which in- 
volves simultaneous CD4 and CDS expression be- 
fore differentiation into single CD4^ or CD8^ cells. 
Although the avian TCR genes are not cloned yet, 
the available biochemical and biological evidence 
suggests that TCR2 and TCR3 represent ap sub- 
classes and implies the sequential utilization of dif- 
ferent sets of P-chain genes. This conclusion, if 
correct, may predict an analogous developmental 
PUBLICATIONS 
sequence in the generation of the ap TCR reper- 
toire in mammals. 
Chick-quail chimeras, created by embryonic trans- 
plants of thymus or other lymphoid organs, were 
used to make several interesting observations. The 
first wave of progenitor cells that enter the thymus 
gives rise to all three T cell sublines. The TCRl, -2, 
and -3 sublines are generated exclusively in the thy- 
mus but may recirculate from the periphery to the 
thymus medulla. A third lineage of lymphocytes, 
which express a CD3 antigen in the cytoplasm and 
CDS on the surface, develops independently of the 
thymus and the bursa. The nature and evolution of 
these TCRO cells are being examined. 
III. IgA Receptor. 
A surface receptor for IgAj and IgA^ antibodies 
has been identified on monocytes and macro- 
phages. ThisM^ 62,000 molecule has been purified, 
and its molecular characterization is in progress. 
Dr. Cooper is also Professor of Pediatrics, Medi- 
cine, and Microbiology at the University of Alabama 
at Birmingham. 
Books and Chapters of Books 
Butler, J.L., and Cooper, M.D. 19S9. Antibody deficiency diseases. In The Metabolic Basis of Inherited Dis- 
ease (Scriver, C.R., BeaudeF, A.L. , Sly WS., and Valle, D. , Eds.). New York: McGraw-Hill, pp 26S3-2696. 
Cooper, M.D., and Burrows, PD. 19S9. B cell differentiation. In Immunoglobulin Genes (Honjo, T, Alt, F.W , 
and Rabbits, T, Eds.). London: Academic, pp 1-21. 
Lawton, A.R., and Cooper, M.D. 1989. Ontogeny of immunity. In Immunologic Disorders in Infants and 
Children (Stiehm, E.R., Ed.). Philadelphia, PA: Saunders, pp 1-14. 
Articles 
Borzillo, G.V, Cooper, M.D., Bertoli, L.F., Landay, A., Castleberry, R., and Burrows, RD. 19SS. Lineage and 
stage specificity of isotype switching in humans. J Immunol 141-3625-5655 ■ 
Bucy R.R, Chen, C.-L.H., Cihak, J., Losch, U., and Cooper, M.D. 19S8. Avian T cells expressing -y6 receptors 
localize in the splenic sinusoids and the intestinal epithelium. J Immunol 141:2200-2205. 
Bucy, R.P, Chen, C.-L.H., and Cooper, M.D. 19S9. Tissue localization and CDS accessory molecule expression 
of T78 cells in humans, f Immunol 142:3045-3049. 
Burrows, RD., Kubagawa, H., and Cooper, M.D. 19S9. Use of Epstein-Barr virus in the analysis of human 
B cell development. Cancer Rev 10:19-32. 
Byrne, J.A., Butler, J.L., Reinherz, E.L., and Cooper, M.D. 19S9. Virgin and memory T cells have different re- 
quirements for activation via the CD2 molecule. Int Immunol l(l):29-35. 
Byrne, J.A., Butler, J.L., and Cooper, M.D. 198S. Differential activation requirements for virgin and memory 
T cells. J Immunol 141:3249-3257. 
Continued 
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