Originally, lymphoid cell signal transduction pathways were the sole proper
ty of basic research scientists, but recent discoveries hale shown their mo
ve into the forefront of clinical diagnosis and research. Clinical discover
ies have now contributed significantly to the understanding of immune devel
opmental pathways through the description of natural occurring mutations in
cell surface receptors and cytoplasmic signal transducing molecules. This
article provides an overview of the clinical contribution to signal transdu
ction research.