Question

Adaptive immunity has several features that distinguish it from innate immunity. Specificity in that each adaptive immune response is induced by a particular antigen, or surface feature that generates an antibody. An innate immune response might be stimulated by a PAMP, while an adaptive immune response is stimulated by a single feature of a bacteria. In addition, cells of adaptive immunity, B and T cells, are allowed to proliferate under certain conditions to mount a defense, this feature is clonality The adaptive immune system is tuned to be unresponsive to self antigens, usually although autoimmune diseases which are many times more common in women, may result from blurred distinctions between self and nonself. In addition, because some differentiated B and T cells are allowed to survive kiss of death that follows cell proliferation after an initial contact with an antigen. These are memory cells that may multiply rapidly on second contact with an antigen with the benefit of differentiation.

1. Describe a B cell and a T cell based on its distinctive cell surface markers or receptors. p476-479

Antibodies are free immunoglobulins not attached to membranes. Ab are peptides with two heavy chains and two light chains joined by disulfide bridges. The Ab stem is the lower portion of the two heavy chains, this is also called the constant fragment (Fc). The arms of the Ab contain the antigen binding site, or Fab. The primary function of an Ab is to bind to an antigen. Once an Ab-Ab complex is formed there are five possible outcomes that help with immune responses.

1. Activation of complement and inflammation. For example IgE might bind to an Ag with its antigen binding sites and use the stem to bind to a mast cell stimulating the release of inflammatory factors.

2. Neutralization, for example Ab can bind to a virus and prevents its attachment to a cell.

3. Agglutination is the aggregation of multiple Ab-Ag complexes with Ab bound to two different Ag, since each Ab has two antigen binding sites.

4. Antibodyd dependent cell mediated cytotoxicity in which the stem of Ab bound to antigen on a microbes surface bind to natural killer cells which then utilize the perforin-granzyme pathway to induce apoptosis in the microbe.

5. Opsonization when Ab act as opsonins to enhance phagocytosis.

2. Would an Ab be effective at interrupting viral synthesis once the virus has entered a cell? Why or why not?

Answer 1

No, once a virus has entered in the cell then antibody cannot interrupt its synthesis. As the virus begins two of the life cycles either lytic or lysogenic. If doing lytic it multiplies into host cells and then the cell burst to release the viruses.

If it begins with lysogenic life cycle then it integrates inside the host's DNA then replicates releasing the proviruses. So, in both the cases, it will divide eventually antibodies cannot stop its replication.

Now the virus-infected cell can produce cytokine-like interferons which will eventually protect the uninfected cells.