Journal of Experimental Medicine, Vol 156, 1635-1649, Copyright © 1982 by Rockefeller University Press
Definition of conditions that enable antigen-specific activation of the majority of isolated trinitrophenol-binding B cells
JC Cambier, JG Monroe and MJ Neale
In an effort to further elucidate the early cellular events in generation
of antibody responses, we have determined the requirements for
antigen-specific initiation of the G0 to G1 transition by isolated
trinitrophenol (TNP) -binding B lymphocytes. TNP-binding cells were
isolated from normal B6D2F1 splenocyte populations using hapten affinity
fractionation on disulfide-bonded TNP-gelatin-coated plates. Populations
prepared in this way are greater than or equal to 96% immunoglobulin
positive and 70-95% antigen binding. Isolated cells were cultured for 48 h
in the presence of a variety of TNP conjugates including TNP-Brucella
abortus (Ba), TNP-Ficoll, TNP-sheep erythrocytes (SRBC), TNP-human gamma
globulin (HGG), or TNP-ovalbumin (OVA) before being harvested and subjected
to acridine orange cell cycle analysis. As many as 80% of cells were in
cycle by 48 h in response to TNP-Ba, a thymus-independent (TI1 antigen. A
smaller proportion (congruent to 40%) were in cycle in response to
TNP-Ficoll, a TI2 antigen. Significant activation was not detected in
cultures challenged with the thymus-dependent immunogens TNP-SRBC, TNP-HGG,
and TNP-OVA. Addition of interleukin 1 (IL-1), IL-2, B cell growth factor,
and/or T cell- replacing factor to cultures did not facilitate responses to
these immunogens, suggesting a requirement for antigen-specific T cell help
for entry into cell cycle induced by thymus dependent antigens. Activation
by TNP-Ba was antigen specific and independent of accessory cells,
occurring with equal efficiency in bulk and single-cell cultures.
Activation by TNP-Ba was inhibitable by anti-Fab and anti-mu antibodies,
but not by anti-delta antibodies. Results indicate that activation of
TNP-binding cells to enter cell cycle by TNP-Ba is independent of accessory
cells and requires interaction of antigen with cell surface IgM. Exposure
to thymus-dependent TNP-immunogens plus nonspecific helper factors is
insufficient to cause entry of TNP- binding cells into cycle.
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