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Characterization of lectin isolated from Momordica charantia seed as a B cell activator

2008; Elsevier BV; Volume: 121; Issue: 2 Linguagem: Inglês

10.1016/j.imlet.2008.10.004

1879-0542

Li Huang, Takumi Adachi, Yuya Shimizu, Yoshitaka Goto, Jun Toyama, Hidenori Tanaka, Ryo Akashi, Akira Sawaguchi, Hiroyuki Iwata, Takeshi Haga,

Glycosylation and Glycoproteins Research

Lectin isolated from the seeds of Momordica charantia (MCL) is a galactose-specific glycoprotein. To investigate the effects of MCL on cell activation, we analyzed the responses of BALB/c splenocytes, thymocytes, T cells and B cells on MCL stimulation. Proliferation assays showed that MCL selectively stimulates the B cell subset of splenocytes (p < 0.05) in a dose and time dependent manner and that this activation proceeds without the involvement of T cells. Flow cytometric analysis revealed that the fluorescein isothiocyanate (FITC)-labeled MCL binds to B cells, which was inhibited by specific sugars, including galactose. Mouse immunoglobulin (Ig) was able to inhibit MCL-induced proliferation of mouse B cells, suggesting MCL stimulates B cell activation via membrane Ig in the B cell surface. Moreover, after 96-h co-culture, MCL triggered splenocytes to produce a large amount of non-specific IgM in culture supernatants (p < 0.01). Additionally, MCL was shown to up-regulate the cell activation marker CD86, in a B cell subpopulation distinct from that affected by LPS. These data suggest that MCL is a T cell-independent B cell activator and a polyclonal Ig inducer, and provide further information on the immunomodulatory effect of MCL.