Isolation by electrofocusing of two lymphocyte mitogens produced by Staphylococcus aureus

Area of Science:

• Microbiology
• Immunology
• Biochemistry

Background:

• Staphylococcus aureus is a common bacterium with various secreted products.
• Lymphocyte mitogens are substances that stimulate cell division in lymphocytes, crucial immune cells.
• Understanding bacterial mitogens can reveal insights into host-pathogen interactions and immune responses.

Purpose of the Study:

• To isolate and characterize extracellular lymphocyte mitogens produced by Staphylococcus aureus strain DA352.
• To investigate the properties and potential modulators of these bacterial mitogens.

Main Methods:

• Culturing Staphylococcus aureus strain DA352 in Todd-Hewitt broth diffusate.
• Separating and purifying mitogens using isoelectric focusing and ethanol precipitation.
• Assessing mitogenic activity through dose-response curves and lymphocyte transformation assays.
• Evaluating the effect of human gamma globulin on mitogen activity.

Main Results:

• Two distinct extracellular lymphocyte mitogens were isolated, with isoelectric points of 5.5-5.7 and 8.6-9.0.
• Mitogens were purified free of other staphylococcal products via ethanol precipitation and isoelectric focusing.
• Both mitogens induced maximal lymphocyte transformation (90%+) comparable to phytohemagglutinin (PHA).
• Mitogenic activity decreased with excess mitogen and showed a slightly less steep dose-response slope than PHA.
• The basic mitogen's activity was enhanced by incubation with undigested or pepsin-digested human gamma globulin.

Conclusions:

• Staphylococcus aureus strain DA352 produces at least two potent lymphocyte mitogens.
• These mitogens exhibit dose-dependent activity on lymphocyte proliferation, similar to PHA.
• The enhancement of the basic mitogen by gamma globulin suggests a potential interaction with host immune components.