A common form of allergy is immediate hypersenstivity, or type I hypersensitivity. This response to an allergen usually occurs relatively quickly (~ 30 mins) and can be very severe. Such a hypersensitivity (aka allergy) is mediated in two distinct steps. First is the sensitization stage where the allergen penetrates, most likely at a skin or mucosal interface, and is taken up by dendritic cells (DC), which are known for there extensive processes and ability to showcase a pathogen on their surface. Next, the DC activates a helper T cell and helps produce a polarized response, meaning the T cell develops into a Th2 subtype. A danger signal must be present in order for this type of activation to occur, but the whereabouts of such a signal is still under debate. Nevertheless, the Th2 cell, known for aiding in the humoral (antibody response) does its duty and activated B cells. These B cells ultimately undergo a process dubbed isotype switching where the type of antibody they produce is modified. This process leads to B cells producing large quantities of a type of antibody known as IgE, known for its role in allergies.
The next stage is the effector stage where if the allergen returns to the body it leads to an allergic response. The IgE antibodies can bind to the outer surface of certain leukocytes, such as mast cells, via Fc receptors and "arm" them. When the allergen returns then the mast cell is activated via the antibodies and degranulates, spewing toxic chemicals at the allergen and causing an immune response in the process.
In the recent work of Morin et al. (2011), the group examines the allergenicity of two proteins found in different fractions of cow milk, beta-lactoglobulin (BLG) and casein (CAS). Cow's milk allergy (CMA) is very common during early childhood and evokes a rapid response. However, CMA usually disappears , it remains in some (Sicherer et al. 2010). What is more dangerous about CMA is that it increases the child's susceptibility to other allergies (Saarinen et al. 2005). In this study, they examined the allergenic and immunogenic effects of these two proteins in two different strains of mice, one was germ-free (GF) and the other conventionally raised (CV). They attempted to complete this study in the absence of an adjuvant for the proteins. Adjuvants are commonly used to give the immune system a push, so to speak, helping to evoke an immune response to the injected compound. The downside of adjuvants in allergy studies is that they can evoke non-specific allergies to some of their own components, making it difficult to examine the specificity of a response. The GF mice have an immature immune system due to their lack of experience with many pathogens, so the authors hypothesized these mice would be more susceptible to an allergic response. Two sets of experiments were completed in each mouse, one measuring antibody type from blood samples and the other examining cytokine secretion from the isolated and reactivated spleens of the mice. Afterwards, they tried something novel and intraperitoneally administered a heated mix of the proteins, hoping to denature the proteins and open new epitopes for binding.
