Question

The immune system responds differently to pathogens that infect intracellularly, such as viruses, than it does when responding to extracellular pathogens, like most bacteria.

The MMR vaccine is a combination vaccine used against three viruses. Our bodies develop immunity through a series of steps that result in the activation of cytotoxic T cells against virally-infected cells. Place the following steps for T cell activation in the correct order.

First Step to Last Step:

Options:

A helper T cell binds to
the MHC-II protein of
an infected dendritic cell.

The dendritic cell secretes
IL-12 to differentiate
the helper T cell into
a type 1 helper T cell.

Dendritic cells infected with
the virus migrate to
lymph nodes.

Activated cytotoxic
T cells undergo
clonal expansion.

The type 1 helper
T cell secretes IL-2
to activate the cytotoxic
T cell.

Activated cytotoxic
T cells self-stimulate
and leave the lymph node.

A cytotoxic T cell binds to
the MHC-I protein of
an infected dendritic cell.