Video Transcript
HIV infects and destroys T-helper
cells. How would an HIV infection affect
the body’s antibody response to a new bacterial infection? (A) Fewer antibodies would be
produced by B cells. (B) There would be no effect on the
antibody response. (C) The same level of antibodies
would be produced, but it would take longer. (D) The antibody concentrations
would rise higher and faster. (E) Only one type of antibody would
be produced.
HIV stands for human
immunodeficiency virus, which is a blood-borne pathogen that, over time, can lead to
acquired immunodeficiency syndrome, called AIDS. The term “immunodeficiency”
describes a situation in which the immune system is not fully functioning. Now, let’s see how the destruction
of T-helper cells affects the body’s antibody response to a new bacterial
infection.
T-helper cells are a type of
lymphocyte that plays a role in the specific immune response. They are also known as CD4-positive
cells because they present a certain protein called CD4 that serves as a coreceptor
for the T-cell receptor. When the complex formed by the TCR
and the CD4 recognizes and binds with a specific antigen presented by the MHC
molecule of a phagocyte, the T-helper cell becomes activated.
Once activated, T-helper cells go
through the process of clonal expansion, increasing the population of activated
T-helper cells that recognize this particular antigen. These activated helper T cells
release cytokines, such as interleukin, to activate B cells and cytotoxic T
cells. Cytotoxic T cells recognize host
cells that are infected with the virus and destroy them.
On the other hand, when activated,
B cells clone themselves and transform into plasma cells that release
antibodies. Note that the activation of B cells
does not always require cytokines from helper cells. Thanks to their specific
antigen-binding activity, these antibodies help to fight the pathogen in various
ways.
Since HIV infects T-helper cells
and destroys them, this often causes a lack of T-helper cells to become
activated. And thus, not enough cytotoxic
cells and B cells can get activated to fight infections effectively. We can now select the correct
answer, which is answer (A). An HIV infection will affect the
body’s antibody response to a new bacterial infection because fewer antibodies would
be produced by B cells.
