Direct interaction between an antigen-specific B cell clone and an MHC class II-reactive helper T cell clone

Area of Science:

• Immunology
• Cell Biology

Background:

• TP67.14 is a 2,4,6-trinitrobenzenesulfonic acid (TNP)-specific B cell clone.
• MS202 is an interleukin-2 (IL-2)-dependent T helper (Th) cell clone reactive to auto-MHC class II antigens.

Purpose of the Study:

• To investigate the mechanism by which MS202 induces the maturation of TP67.14 into anti-TNP plaque-forming cells (PFCs).
• To determine the role of cell contact versus soluble factors in Th-B cell interaction for B cell maturation.

Main Methods:

• Co-culture of TP67.14 and MS202 cells.
• Use of semipermeable membranes to separate cell cultures.
• Treatment with recombinant cytokines, monoclonal antibodies (anti-IL-4, anti-IL-5, anti-LFA-1 beta, anti-IAk, anti-IEk).
• Analysis of plasma membrane-enriched fractions (PM) from MS202.

Main Results:

• MS202 significantly induced TP67.14 maturation into anti-TNP PFCs, augmented by TNP-keyhole limpet hemocyanin (KLH).
• This effect was dependent on direct cell contact, as it was lost when cells were cultured separately.
• Monoclonal antibodies against LFA-1 beta, IAk, and IEk blocked the maturation process.
• Plasma membrane-enriched fractions from MS202, especially when conjugated with TNP, induced significant anti-TNP PFC formation.

Conclusions:

• Th cells induce B cell maturation into antibody-secreting cells through direct cell contact, not soluble factors.
• Surface major histocompatibility complex class II and lymphocyte function-associated antigen 1 molecules on Th cells are critical for this interaction.
• Th cell membrane components provide a signal for B cell maturation in the presence of antigen.