Microtubule assembly and conanavalin A capping in lymphocytes: reappraisal using normal and abnormal human peripheral blood cells.

We have analyzed the assembly of microtubules and the distribution of concanavalin A(Con A)-receptor complexes in the same populations of human peripheral blood T and B lymphocytes. We hoped to resolve the prolonged controversy over the relationship of microtubules to Con A cap formation in lymphocytes and to explain the abnormally high spontaneous and colchicine-induced Con A capping that was observed recently in lymphocytes from a patient with an inherited form of severe combined immunodeficiency disease (SCID) characterized by total immunologic dysfunction despite normal numbers and distribution of T and B cells. The data establish that (i) microtubule disassembly is correlated with enhanced Con A cap formation on normal human lymphocytes; (ii) T and B cells differ significantly from each other and from circulating polymorphonuclear leukocytes with respect to their capping responses after exposure to colchicine; and (iii) there is an abnormal relationship of microtubule assembly to surface topography in the functionally defective SCID cells.