Parasitic and Fungal Infections and the Immune System

These flashcards cover Page 1 through Page 15 of the lecture notes, including parasitic and fungal infections, genetic disorders related to infection resistance (SCA), STDs, and the components and mechanisms of the innate and adaptive immune systems.

How do fungal and parasitic infections generally differ in their occurrence?

Fungal infections are usually opportunistic, while parasitic infections affect billions of people worldwide.

What are the two common stages in the life cycle of protozoan parasites?

The dormant "cyst" stage (formed in unfavorable conditions) and the active "trophozoite" stage (feeding/reproduction stage inside the body).

Which protozoan and vector are responsible for malaria?

Malaria is caused by Plasmodium spp. and is transmitted by the Anopheles spp. mosquito.

List the potential physiological consequences of a malaria infection.

Anemia (from destruction of RBCs), fever, hypotension (low BP), jaundice (liver failure), renal failure, and brain damage.

In the life cycle of Plasmodium, what are the definitive and intermediate hosts?

The definitive host is the mosquito (sexual reproduction) and the intermediate host is the human (asexual reproduction).

Which malaria medication is noted for causing psychological side effects?

Mefloquine ("Lariam").

What is a "lateral flow immunochromatographic assay"?

A diagnostic test used to detect the presence or absence of a target (antigens or antibodies) in a sample, such as in pregnancy or malaria tests.

Define antigens and antibodies.

Antigens are molecules that trigger an immune response (e.g., proteins on a microbe surface); antibodies are proteins produced by the immune system that bind specifically to antigens.

What characterizes the red blood cells in Sickle Cell Anemia (SCA)?

They contain abnormal hemoglobin, take on a rigid, sickle-like shape, and live for only about $10\,\text{days}$.

Why is Sickle Cell Anemia considered advantageous in areas where malaria is prevalent?

Sickle RBCs do not harbor the parasite well, providing resistance to malaria infection; this is known as "heterozygous advantage."

What are the three possible genotypes for the SCA mutation?

Homozygous Dominant ($SS$), Heterozygous dominant ($Ss$), and homozygous recessive ($ss$).

How is Toxoplasma gondii typically transmitted to humans?

Via fecal contamination (fecal-oral route), such as cleaning a cat litter box.

What protozoan causes amebiasis and what is the recommended treatment?

Entamoeba histolytica; treated with metronidazole ("Flagyl") and fluid replacement therapy (ORT).

List five symptoms of severe dehydration.

Headache, weakness, sunken eyes, poor skin turgor (slow to spring back), and tachycardia (rapid heart rate).

What is the difference between diarrhea, dysentery, and gastroenteritis?

Diarrhea involves loose stools; dysentery involves bloody diarrhea; gastroenteritis involves diarrhea with major abdominal pain and fever.

What are the characteristics of Trichomonas vaginalis?

It is a protozoan parasite with 5 flagella, has no "cyst" phase in its life cycle, and causes the STD trichomoniasis.

Distinguish between the two types of Trypanosomiasis.

African Sleeping Sickness is caused by Trypanosoma brucei (tsetse fly); American Chagas disease is caused by Trypanosoma cruzi (kissing bug).

What physical signs are associated with Sleeping Sickness and Chagas disease?

Winterbottom’s sign (swollen lymph nodes in the neck) is for Sleeping Sickness; Romana signs (swollen eyelids) is for Chagas disease.

How are pinworms (enterobiasis) typically spread among children?

Children ingest eggs via contaminated food or hands and then re-infect themselves or others by scratching the itchy anal area.

What are the three stages of Syphilis infection?

Primary (chancres/painless sores), Secondary (maculopapular rash on palms/face), and Tertiary (gummas, brain damage, and neurosyphilis).

What is the most common "nationally reported" STD and what bacteria causes it?

Chlamydia, caused by Chlamydia trachomatis.

What are the clinical manifestations of Genital Herpes?

Vesicular lesions (fluid-filled blisters) on the genitals, caused by HSV-2 or occasionally HSV-1.

At what threshold is a person with HIV considered to have AIDS?

When their CD4 T cell count is less than $200\,\text{cells/}\mu\text{L}$ of blood.

What are the three physical defenses of the skin in the innate immune system?

It is impenetrable to most microbes, dry, acidic, and removes microbes through sloughing.

What is the function of lysozyme in the immune system?

It is an enzyme found in tears, saliva, and perspiration that destroys peptidoglycan in bacterial cell walls.

Describe the three types of T cells in adaptive immunity.

Helper T cells (TH) stimulate B cells and have CD4 receptors; Cytotoxic T cells (TC) destroy infected host cells and have CD8 receptors; Regulatory T cells control the overall response and have CD4 receptors.

By what three mechanisms do antibodies defeat microbes?

Neutralization (prevents adhering), Opsonization (promotes phagocytosis), and Complement activation (kills microbes).

Define "Central Tolerance" and "Clonal Selection."

Central Tolerance is the destruction of cells that produce antibodies against self-antigens; Clonal Selection ensures only beneficial antibody-producing cells are replicated.

What happens in Multiple Sclerosis (MS)?

The immune system attacks the protective covering on nerves known as the myelin sheath.

Contrast atopic and anaphylactic allergies.

Atopic allergies are chronic and localized (e.g., Asthma); Anaphylactic allergies are sudden, rapid, and systemic (e.g., bee sting shock).