I have an immunology question for you guys. Any help would be great! In an examp

Question

I have an immunology question for you guys. Any help would be great!

In an example of a precipitin reaction experiment, we are told that the researchers noticed that even though the hapten alone (DNP) was unable to elicit an immune response from an immunized rabbit, the response induced by the hapten-carrier conjugate (DNP10-BSA) clearly included antibodies specific for DNP per se. Interestingly, this is a seemingly counterintuitive phenomenon. Understanding the requisites for T cell antigen recognition and activation, as well as an understanding of a B cell's needs, provide a satisfactory (and hopefully somewhat more sophisticated/detailed) explanation for why one cannot get a humoral response against DNP alone but can get a response to it when coupled to a carrier.

Explanation / Answer

Generally an antigen presenting cell (APC), helper cell and an effector cell together interact to generate an immune response. In normal sequence, the macrophage or dendritic cell is an antigen presenting cell presents antigen to T helper cell and binds to class II MHC molecules and then present antigen to T cytotoxic cell that neutralizes the antigen.

In humoral immune response, The TH2 helper cell along with class II MHC molecule attached to CD4 or CD8 along with antigen binds to T cell receptor that is recognized by IL 4 and B7 cells co- stimulate the memory TH2 cell to produce antibody against the antigen accomplishes the three cell interaction.

The B cell interaction with antigen is mediates by precommitted memory B cells that recognize a specific epitope on antigen surface and binds to surface Ig molecule. Then the B cell internalizes the antigen through receptor mediated endocytosis. It also degrades the peptide carrier molecule (classII MHC) and produces a new classII MHC molecule on the surface.

The TH cells pre-committed to neutralize antigen would recognize the antigen through the carrier epitope molecules and through carrier determinant Class II molecules by T cell receptors. Thus, clonal selection and T cell B cell cooperation is important in generating an immune response.

B cell and T cell response towards an antigen depends on hapten and carrier concept. In a strict sense hapten is a chemical moiety of a carrier molecule recognized by B cell and produces immune response or antibodies. Even if the carrier molecule fragment binds to the B cell antibody is generated against the antigen - carrier complex. DNP is such carrier molecule that can be recognized by B cell.

However, DNP is not a peptide molecule that can be recognized by T cell antigen presenting cell class II MHC molecule. Thus, antibodies produced by B cells can bind to haptens like DNP as well as large protein carrier molecules while, T cells recognize only peptides associated with class II MHC molecules by T cell receptors.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.