A novel mitogen released by lipid A-stimulated bone marrow cells

Area of Science:

• Immunology
• Cell Biology

Background:

• Lipopolysaccharide (LPS) is a key component of Gram-negative bacteria.
• LPS responsiveness varies significantly between different mouse strains, such as C3H/HeN (responder) and C3H/HeJ (nonresponder).
• Bone marrow cells and splenocytes are critical components of the immune system involved in cellular responses.

Purpose of the Study:

• To investigate the interaction between Lipid A and bone marrow cells.
• To identify the factor released by stimulated bone marrow cells.
• To determine the cellular target of this released factor in nonresponder mice.

Main Methods:

• Lipid A stimulation of bone marrow cells from C3H/HeN mice.
• Assessing DNA synthesis enhancement in C3H/HeJ splenocytes.
• Autoradiography and immunofluorescence to identify responding cells.
• Biochemical characterization of the mitogenic factor (heat, trypsin, RNase sensitivity).

Main Results:

• Lipid A-induced bone marrow cells released a factor enhancing DNA synthesis in C3H/HeJ splenocytes.
• This mitogenic effect was not observed with C3H/HeN splenocytes.
• The target cells were identified as B cells expressing surface immunoglobulin.
• The factor was determined to be heat-labile, trypsin-sensitive, and RNase-insensitive.

Conclusions:

• Bone marrow cells from LPS-responder mice produce a B-cell mitogen in response to Lipid A.
• This mitogen acts on B cells from LPS-nonresponder mice, suggesting a mechanism for immune modulation.
• The factor's properties indicate it is likely a protein.