Question

Assume that a drop in parasite abundance reflects an effective immune response by the host. Formulate a hypothesis to explain the pattern you described in question 2.

Short answer

When the host's immune response to the first surface glycoprotein was effective, the parasite shifted to a new one. This explains why parasite counts fluctuate over time in cycles.

Step-by-step solution

Immune response

The immune system identifies antigens (typically proteins) on the surface of substances or bacteria and attacks and destroys them in an immune response. The immune system has specific immune cells that enable it to respond specifically to certain targets.

Depending on whether the target has already penetrated the body, it may adjust the speed and aggressiveness of its reaction.

Glycoprotein

Glycoprotein is the protein that is covalently linked to carbohydrates. Cells contain large amounts of these molecules, which serve as enzymes, hormones, transport proteins, structural proteins, and receptors, among other functions.

Glycoproteins are membrane proteins that play an important role in cell-cell interactions, as well as the host's pathogenic response.

Glycoprotein on trypanosome

A trypanosome's glycoprotein coat is encoded by a gene that has been replicated over 1,000 times in its genome. By switching between these genes regularly, the trypanosome can display a variety of surface glycoproteins with various molecular structures.

African trypanosomes have a variable surface glycoprotein (VSG) coat that shields them from lytic factors in human plasma and helps them to evade the host immune response.