The specialist caterpillars of the monarch butterfly

(Danaus plexippus) are insensitive to the terpenoid toxins. They feed on milkweed leaves and retain the cardenolides. As a result, most insectivorous birds quickly learn to avoid eating monarch caterpillars and adult monarch butterflies.

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.

TLS Online TPP Program

#Id: 1721

#Unit 4. Cell Communication and Cell Signaling

Monocytes and platelets express an alternative form lacking the β chain.

TLS Online TPP Program

#Id: 1722

#Unit 4. Cell Communication and Cell Signaling

The α chains of the FcεRI, members of the immunoglobulin superfamily, directly bind the IgE heavy chains, whereas the β and γ chains are responsible for signal transduction.