PARA Practice test knowt

Explain how symbiotic bacteria Wigglesworthia contributes to tsetse fly immunity

• Wigglesworthia are intracellular parasites of tsetse flies that infect near the midgut of the fly

• These bacteria provide the fly with vitamins that the fly itself cannot produce

• Absence of wigglesworthia leads to decreased expression of anti-microbial peptides and flies are more susceptible to trypanosome infections.

• Wigglesworthia is vertically transmitted to progeny.

What are the three effector functions of compliment activation

1. Opsonization- subunits can promote phagocytosis

2. Inflammation- subunits can recruit inflammatory cells

3. Cell lysis- subunits can aid in formation of membrane attack complex (MAC) and cause cell lysis

Briefly explain why dendritic cells are considered a bridge between innate and adaptive immunity

As part of the innate response, dendritic cells engulf pathogens and complex them with MHC to present antigens on their cell surface. These antigens presented on their cell surface then activate t cells to elicit an adaptive response

2 reasons the cost of absolute immunity may be too high for a host

1. Host tissue damage

2. High energy expenditure

It has been demonstrated that the treatment of cutaneous leishmaniasis can be augmented by direct administra3on of IL-12 into skin lesions. Based on what you have learned about the immune response to this parasite, and the role of IL-12, explain the efficacy of IL-12 treatment

The cytokine IL-12 is involved in activating a Th-1 response which drives cell-mediated immunity. Cell-mediated immunity is more effective against intracellular pathogens like Leishmania. Thus, administration of IL-12 into skin lesions helps to promote cell-mediated immunity and can help in treatment of cutaneous leishmaniasis.

Describe how tuft-cell detection and Th-2 immunity contribute to the intestinal “weep and sweep” response against helminths

• Damaged host cells release cytokines that activate tuft cells to release more cytokines called alarmins that drive the Th-2 response

• Th-2 cells release more cytokines that alter the mucosal epithelium in ways that make it less hospitable for intestinal helminths

What are two specific effects of tuft-cell induced weep and sweep

1. Increased contraction of intestinal smooth muscle dislodges worms and increases peristalsis

2. Increased mucus secretion by intestinal epithelium prevents further attachment and penetration of epithelium by worms

One specific example of how parasites can evade compliment-mediated innate immune responses

Schistosoma mansoni expresses protein SCIP-1 that binds a compliment subunit that prevents formation of the membrane attack complex

What cytokine stimulates Th-1 cells to do what

IL-12 stimulates Th-1 cells to drive cell mediated immunity by releasing IL-2 and IFN-gamma

What cytokine stimulates Th-2 cells to do what

IL-4 stimulates Th-2 cells to drive humoral immunity by releasing IL-4, IL-5, and IL-10

What type of immune response is best for intracellular parasites

Th-1 driven cell-mediated immunity

What type of immune response is best for extracellular parasites

Th-2 driven humoral immunity