Question

1. Fill in the blank:

The ________ of a lymphocyte results in immune cells that have gained the ability to attack specific antigens.

2. How does a virus, such as HIV, typically enter a cell? What structure does the virus use to enter the cell?

3. Explain why we need the mechanisms of the adaptive immune system even though nonspecific or innate resistance mechanisms attack all foreign antigen (in other words, what purpose does the acquired immune system serve?)

Answer 1

1. B-cells of lymphocytes :

B lymphocytes produce antibodies - proteins (gamma globulins) that recognize foreign substances (antigen) and attach themselves to them. B lymphocytes (or B cells) are each programmed to make one specific antibody.

2. When HIV infects a cell, it first attaches to and fuses with the host cell. Then the viral RNA is converted into DNA and the virus uses the host cell's machinery to replicate itself during a process called reverse transcription. The new copies of HIV then leave the host cell and move on to infect other cells.

Virus enters cell by endocytosis. In the cytoplasm, the capsid comes apart, releasing the RNA genome. Replication and gene expression. The RNA genome is copied (this would be done by a viral enzyme, not shown) and translated into viral proteins using a host ribosome.

Although some viruses have the capacity to penetrate into the cytosol directly through the plasma membrane, most depend on endocytic uptake, vesicular transport through the cytoplasm, and delivery to endosomes and other intracellular organelles.

3. Attacking bacteria and viruses directly. Preventing bacteria and viruses from attaching to and invading cells. Activating the complement system, which has many immune functions. Helping certain cells, such as natural killer cells, kill infected cells or cancer cells.

The main purpose of the innate immune response is to immediately prevent the spread and movement of foreign pathogens throughout the body. The second line of defense against non-self pathogens is called adaptive immune response.

The adaptive defense consists of antibodies and lymphocytes, often called the humoral response and the cell mediated response. ... This interaction is so crucial that the adaptive response cannot occur without an innate immune system. The cells of the adaptive immune system are lymphocytes – B cells and T cells.

Explaination -

One of the body's lines of defense (immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and other invaders. (See also Overview of the Immune System.)

This defense has two parts:

• Innate immunity

• Acquired immunity

Acquired (adaptive or specific) immunity is not present at birth. It is learned. The learning process starts when a person’s immune system encounters foreign invaders and recognizes nonself substances (antigens). Then, the components of acquired immunity learn the best way to attack each antigen and begin to develop a memory for that antigen. Acquired immunity is also called specific immunity because it tailors its attack to a specific antigen previously encountered. Its hallmarks are its ability to learn, adapt, and remember.

Acquired immunity takes time to develop after first exposure to a new antigen. However afterward, the antigen is remembered, and subsequent responses to that antigen are quicker and more effective than those that occurred after the first exposure.

The white blood cells responsible for acquired immunity are

• Lymphocytes (T cells and B cells)

Other participants in acquired immunity are

• Dendritic cells

• Cytokines

• The complement system (which enhances the effectiveness of antibodies)