Ig Knock-In Mice Producing Anti-Carbohydrate Antibodies: Breakthrough of B Cells Producing Low Affinity Anti-Self Antibodies

Abstract

Natural Abs specific for the carbohydrate Ag Galα1–3Galβ1–4GlcNAc-R (αGal) play an important role in providing protective host immunity to various pathogens; yet little is known about how production of these or other anti-carbohydrate natural Abs is regulated. In this study, we describe the generation of Ig knock-in mice carrying functionally rearranged H chain and L chain variable region genes isolated from a B cell hybridoma producing αGal-specific IgM Ab that make it possible to examine the development of B cells producing anti-carbohydrate natural Abs in the presence or absence of αGal as a self-Ag. Knock-in mice on a αGal-deficient background spontaneously developed αGal-specific IgM Abs of a sufficiently high titer to mediate rejection of αGal expressing cardiac transplants. In the spleen of these mice, B cells expressing αGal-specific IgM are located in the marginal zone. In knock-in mice that express αGal, B cells expressing the knocked in BCR undergo negative selection via receptor editing. Interestingly, production of low affinity αGal-specific Ab was observed in mice that express αGal that carry two copies of the knocked in H chain. We suggest that in these mice, receptor editing functioned to lower the affinity for self-Ag below a threshold that would result in overt pathology, while allowing development of low affinity anti-self Abs.

Baseline values of immunologic parameters in the lizard <i>Salvator merianae</i> (<i>Teiidae</i>, Squamata)

“…7(2): 143-149 ________________________________________________________________________________________________________ 147 lizards. This increase in NAb with age has been also reported in mammals, birds, and others reptiles (Parmentier et al, 2004;Benatuil et al, 2008;Sparkman and Palacios, 2009;Ujvari and Madsen, 2011;Zimmerman et al, 2013). In reptiles of all ages, the specific antibody response is slower and less robust than in mammalian counterparts (Zimmerman et al, 2010).…”

Humoral immune responses are maintained with age in a long-lived ectotherm, the red-eared slider turtle

“…Thus, our turtles seem to have an increase in NAb, B-1-like immunity with age, but the specific, B-2-like response to LPS was not significantly impacted by age. While an increase in NAbs with age has been reported in mammals, birds and reptiles (Candore et al, 1997;Parmentier et ., 2004;Benatuil et al, 2008;Sparkman and Palacios, 2009;Ujvari and Madsen, 2011), studies in these same taxa have also reported a decrease in specific antibodies with age (Ujvari and Madsen, 2005;Lavoie, 2006;Frasca et al, 2008;Ujvari and Madsen, 2011). These studies on specific immune responses include a wide range of both T-dependent and T-independent antigens, including LPS.…”

“…These new assays, along with the ELISA that we have previously validated and the common practice of using blood smears to examine leukocyte populations, will allow us to gain a fuller understanding of humoral immune responses of sliders. A wide range of studies in a variety of vertebrate taxa, including mammals, birds and reptiles, have found that specific antibodies decrease with age while NAbs increase with age (Candore et al, 1997;Parmentier et al, 2004;Ujvari and Madsen, 2005;Lavoie, 2006;Benatuil et al, 2008;Frasca et al, 2008;Sparkman and Palacios, 2009;Ujvari and Madsen, 2011). This pattern, along with the typically slow and less-robust specific responses of reptiles, leads us to hypothesize that red-eared sliders utilize a predominantly NAbbased response, and thus would not show a deficit in humoral immune defenses with age.…”

Variation in the seasonal patterns of innate and adaptive immunity in the red-eared slider (Trachemys scripta)

“…We did find a positive correlation between plastron length and antibody levels, indicating that at least the humoral branch of the immune system may vary with age in this long-lived species. Although antigen specific immune responses typically decrease with age in mammals (Frasca et al, 2008), natural antibody levels tend to increase with age throughout the lifetime of the individual (Candore et al, 1997;Benatuil, 2008). Natural antibodies are produced by a class of long-lived and self-replenishing B cells known as B-1 cells (Baumgarth et al, 2005).…”