Biology - 2.5 - Part 4 - defence against parasitic attack

Is the immune response in animals specific or non-specific?

It has both specific and non-specific aspects.

What are non-specific defences?

Physical barriers, chemical secretions, inflammatory response, phagocytes, natural killer cells that destroy cells infected with viruses.

What are natural killer cells?

Lymphocytes.

What are specific defences?

Immune surveillance, carried out by a range of white blood cell which constantly circulate and monitor tissues.

What happens when a tissue becomes damaged or invaded?

Cytokines are released, which increases blood flow. This results in non specific and specific white blood cells accumulating at the site of infection or tissue damage.

What are lymphocytes potentially able to do?

Recognise a parasite antigen.

What does each lymphocyte possess?

A receptor on its surface.

Mammals have different types of lymphocytes, name two.

B cells and T cells.

What do B cells do in response to foreign antigens?

They produce proteins called antibodies that are specific in shape to the antigen.

What do T cels do in response to foreign antigens?

They destroy infected or damaged cells by bringing about apoptosis.

What is apoptosis?

Cell death.

What does binding of an antigen to a lymphocytes receptor do?

causes that lymphocyte to divide and then produce a clonal population os this lymphocyte.

What is clonal selection?

Lymphocytes become amplified by dividing. The clones have different uses.

What do the two clones from clonal selection do?

One is used in immediate defence and the other lives longer as a memory cell so that if the individual is exposed to the same parasite, the memory cells can quickly defend.

What regions do antibodies possess?

Variable regions where the amino acid sequence varies greatly between different antibodies.

What gives the antibody its specificity for the binding antigen?

The variable region (differing amino acid sequence).

What does the antigen-antibody complex result in? (parasite)

It results in the inactivation of the parasite, rendering it susceptible to a phagocyte, or it can stimulate a response that results in cell lysis.