Host defence againstC. albicansinfections in IgH transgenic mice with V_Hderived from a natural anti-keratin antibody

Abstract

SummaryFungal infections have been increasing and lifethreatening in recent years, but host immune responses, especially the humoral immunity, to fungi have not been fully understood. In the present study, we report that natural antibodies from unimmunized mice bind to Candida albicans. We established a monoclonal natural antibody, 3B4, which recognized a surface antigen located at germ tubes of C. albicans. The 3B4 antibody protected mice from C. albicans-induced death in passive immunization, by mechanisms involving suppressing germ tube formation and modulating phagocytosis. Interestingly, 3B4 also bound to a self-antigen keratin. To further study the generation and anti-C. albicans activities of natural antibodies in vivo, we constructed a m chain transgenic mouse (TgV H3B4) using the VH gene from 3B4. TgVH3B4 had elevated serum anti-keratin/ C. albicans IgM, and were resistant to C. albicans infections. Analyses of B cell development showed that in TgVH3B4, B cells secreting the anti-keratin/ C. albicans antibodies were enriched in the B1 B cell compartment. Our findings reveal an important role of keratin-reactive natural antibodies in anti-C. albicans immune responses, and suggest that keratin may function in selecting B cells into the B1 B cell compartment, where natural antibodies are made to fight fungal infections.

Complement activation contributes to the anti-methicillin-resistant Staphylococcus aureus effect of natural anti-keratin antibody

“…The m chain transgenic mice (TgV H 3B4) using the V H gene from 3B4 used in this study was kindly provided by Prof. Yufeng Liu (Fourth Military Medical University, Xi'an, China) [14]. The mice in the infection group were administered 0.5 ml of MRSA (10 8 /ml) by intraperitoneal injection.…”

“…The monoclonal natural anti-keratin antibody IgM was produced as previously described [14]. The clone 3B4, which preferentially recognizes keratin, was used in the present study.…”

“…Natural IgM antibodies have also been reported to protect against microbial infections by recognizing a wide range of different microbial components [6,7]. In a previous study, we reported a monoclonal natural antibody, 3B4, which was isolated from the serum of a unimmunized mice [14]. We demonstrated that 3B4 recognized keratin and a surface antigen located at germ tubes of Candida Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; Ig, immunoglobulin; FCM, flow cytometry; TgV H 3B4, a m chain transgenic mouse (TgV H 3B4) using the V H gene from 3B4; PLF, peritoneal lavage fluid; MBL, mannose-binding lectin; NMS, normal mouse serum; CFU, colony-forming units; MgEGTA, magnesium ethylene glycol tetra-acetic acid; TMB, 3,3 0 ,5,5 0 -tetramethylbenzidine; HRP, horse reddish peroxidase; IL, interleukin; TNF, tumor necrosis factor; IFN, interferon; BSA, bovine serum albumin.…”

“…3B4 inhibited germ tube formation of C. albicans in vitro and protected mice from C. albicans-induced death in vivo [14]. We also established a m chain transgenic mouse (TgV H 3B4) using the V H gene from 3B4, and demonstrated that this mice possessed high level of anti-keratin/ C. albicans IgM antibodies and were resistant to C. albicans infections [14].…”

“…We demonstrated that 3B4 recognized keratin and a surface antigen located at germ tubes of Candida Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; Ig, immunoglobulin; FCM, flow cytometry; TgV H 3B4, a m chain transgenic mouse (TgV H 3B4) using the V H gene from 3B4; PLF, peritoneal lavage fluid; MBL, mannose-binding lectin; NMS, normal mouse serum; CFU, colony-forming units; MgEGTA, magnesium ethylene glycol tetra-acetic acid; TMB, 3,3 0 ,5,5 0 -tetramethylbenzidine; HRP, horse reddish peroxidase; IL, interleukin; TNF, tumor necrosis factor; IFN, interferon; BSA, bovine serum albumin. albicans, and the isotype of 3B4 was IgM [14]. 3B4 inhibited germ tube formation of C. albicans in vitro and protected mice from C. albicans-induced death in vivo [14].…”