A third set of maternal genes whose proteins generate the unsegmented extremities of the anterior-posterior axis: the acron (the terminal portion of the head that includes the brain) and the telson (tail).

TLS Online TPP Program

#Id: 1715

#Unit 4. Cell Communication and Cell Signaling

Properties of allergens

 a. Allergens are either protein or glycoprotein in nature, with multiple antigenic sites.

 b. Many allergens have intrinsic enzymatic activity that affects the immune response.

c.  Many allergens contain potential pathogen associated molecular patterns.

d.  Many allergens enter the host via mucosal tissues at very low concentrations, which tend to predispose the individual to generate TH2 responses, leading to B-cell secretion of IgE.

TLS Online TPP Program

#Id: 1716

#Unit 4. Cell Communication and Cell Signaling

The serum half-life of IgE is quite short (only 2 to 3 days). However, when bound to its receptor on an innate immune cell, IgE is stable for weeks.

TLS Online TPP Program

#Id: 1717

#Unit 4. Cell Communication and Cell Signaling

IgE binds two different receptors, the high-affinity FcεRI, which is responsible for most of the symptoms we associate with allergy, and the lower-affinity FcεRII, which regulates the production of IgE by B cells, as well as its transport across cells.

TLS Online TPP Program

#Id: 1718

#Unit 4. Cell Communication and Cell Signaling

FcεRI, which binds IgE with an exceptionally high-affinity constant of 10^10 M^-1 .

TLS Online TPP Program

#Id: 1719

#Unit 4. Cell Communication and Cell Signaling

The other IgE receptor, designated FcεRII, or CD23, has a much lower affinity for IgE (Kd of 1 * 10 6 M -1 )

TLS Online TPP Program

#Id: 1720

#Unit 4. Cell Communication and Cell Signaling

Most cells express a tetrameric form of FcεRI, which includes an α and β chain and two identical disulfide-linked γ chains.