CYTOTOXICITY

 

Cytotoxicity just means 'toxic to cells'.

Cytotoxic cells are those cells that kill micro-organisms directly by chemical means, but do not phagocytose their victims.

In other words, they indulge in chemical warfare.

In the innate/non-specific immune response to infection, there 2 types of cytotoxic activity that are important.

One type requires antibodies/opsonins to be bound to the victim, whilst the other one does not.

Cytotoxic activity in the absence of antibodies is carried out by eosinophils and natural killer (NK) cells.
REFLECTION

Now is a good time just to look a little more closely at eosinophils:
Eosinophils  make up 1-3% of white blood cells in the blood stream.
Like the neutrophils, eosinophils have numerous intracellular 'granules' containing the bactericidal enzymes and toxic proteins which can perforate the membranes of micro-organisms.
A major role of the eosinophils, which relates to non-specific/innate immunity, is to inflict damage on multi-cellular parasites, such as worms and flukes that are too large to be phagocytosed.
The way in which eosinophils inflict damage on internal parasites is by sending out a burst of oxidising agents as degradative enzymes onto the surface of the target organism - in other words, they can kill them from a distance; this process can then destroy these large organisms.

 

(Note that degradative = breaking down/disintegrating)

 

 

The second type of cytotoxic action is known as antibody-dependent cell-mediated cytotoxicity (ADCC) - but, as the name suggests, this requires the presence of antibodies (a product of the acquired/specific immune system).

This is carried out by a type of cell called the LARGE GRANULAR LYMPHOCYTE (a cell that is similar to the NK cell).