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The F(ab')2 fragment of rabbit anti-human F(ab')2 antibodies covalently linked to polyacrylamide beads (anti-Ig beads) acts as a polyclonal mitogen for human B cells in whole peripheral blood mononuclear cells (PBM) or tonsil cells. Activation, measured by the rate of DNA synthesis, is the result of an interaction between the anti-Ig beads and membrane immunoglobulin found on B cells. Excess soluble human F(ab')2 blocks activation with anti-Ig beads. Immunospecifically purified antibodies against IgM or IgD bound to beads activate lymphocytes. Also soluble anti-IgM or anti-IgD can block activation with insolubilized anti-IgM or anti-IgD, respectively, by modulating membrane immunoglobulin. Irrelevant rabbit antihapten antibodies bound to beads failed to activate PBM or tonsil cells. Anti-Ig beads act independently of T cells. The anti-Ig beads lead to activation of B cells without further maturation to polyclonal immunoglobulin secretion.

Mononuclear cells (10--20 X 10(6)) obtained from human peripheral blood by a standard Ficoll-Hypaque technique were suspended in RPMI 1640 media at 4 degrees C containing 10% foetal calf serum and 7-5% dimethyl sulphoxide (DMSO). Two-millilitre aliquots were cooled at -1 degree C/min in a Cryoson BV-4 programmed freezing system to -30 degrees C, then -5 degrees C/min to -80 degrees C and stored in liquid nitrogen vapor. On the day of testing, cell suspensions were thawed rapidly in a 37 degree C water bath. DMSO was diluted slowly out of the sample and cells resuspended in fresh RPMI 1640. It was found that frozen stored human lymphocytes (FSHL) demonstrated all the characteristics of fresh unfrozen cells. These included their ability to form spontaneous rosettes with sheep erythrocytes ('E' rosettes) and sheep erythrocyte--antibody--complement rosettes ('EAC' rosettes). The presence of surface immunoglobulins and Fc receptors were shown by membrane immunofluorescence to be comparable. In addition, the results show that FSHL respond to mitogens, specific antigens; act as both stimulators and responders in the mixed lymphocyte culture reaction; and exhibit cell-mediated lymphocytotoxicity following in vitro sensitization, or against antibody-coated target cells.