Fungal Immunity : part 1

Question 1

Which fungi classes cause disease in humans

Answer 1

3 phyla causing disease in humans Zygomycota Basidiomycota `Ascomycota (bottom 2 more closely related)

Question 2

Give an example of ascomycota

Answer 2

Candida and Aspergillus

Question 3

Give examples of basidiomycota

Answer 3

Mushrooms(cryptococci)

Question 4

List Fungi causing infections

Answer 4

Aspergillus (ascomycota) Cryptococcus (basidiomycota) Candida albicans (ascomycota)

Question 5

How can aspergillus cause problems

Answer 5

Have spores called conidium.Normally fine, most people inhale every day Only a problem if you have no neutrophils Can germinate (leading to fungal ball) and cause bleeding in LUNGS

Question 6

How can Cryptococcus neoformans cause disease

Answer 6

Mushroom group (microscopic) .Fimbrae that allow it to adhere to surfaces .Commonest cause of death in HIV patients (subsaharan Africa) .Inhaled through lungs but can disseminate to brain if lack of CD4+ T cells. Leads to cryptococcal meningitis. Can then develop cryptococcomas (fungal ball) , and stroke like symptoms.

Question 7

What is cryptococcoma

Answer 7

Ball of fungus which has germinated. CNS (cryptococcus neoformans)

Question 8

How can candida albicans cause disease

Answer 8

Candida is commensal on skin and gut But in immunocompromised/catheterised, can develop invasive infeection. Can get into the back of the eye creates mass =candida endophthalmitis, for example

Question 9

Outline cellular immunity to fungal infection

Answer 9

Innate immune system very important. Loss of neutrophils is a key risk factors .Most fungi encountered at mucosal surface (in gut, yeast or on lungs as moulds). Opsonisation, phagocytes and complemet all important. Dendritic cells present antigen to T cells Can lead to Th1, Th2 and Th17 responses(these then determine innate response-circle).

Question 10

Why are NK cells important in cellular immunity to fungal infection

Answer 10

They produce IFN-g which primes macrophage to deal with fungus

Question 11

Outline how fungi change shape Candida, cryptococcus and aspergillus

Answer 11

Can start as unicellular organisms then become mutlicellular ▪Candidal dimorphism (starts of as budding yeast but when it is involved in invasioive infections changes into hyphal forms, which are muticellular filamentoius structurees) allows tissue invasion ▪Crytpococcus divides in the host as a yeast. Forms a capsule to evade phagocytosis ▪Aspergillus species inhaled as conidia, invade tissues as hyphae

Question 12

How can fungi be sensed

Answer 12

Toll like receptors (innate receptor). Losing the toll systems put you at high risk of fungal disease

Question 13

What are c-type lectins

Answer 13

Part of immunoglobulin super family.Detect carbohydrate on fungal cell wall. Important for phagocytosis of fungi (TLR cannot do it alone, need c -type lectins).

Question 14

What receptors are important in fungal infection

Answer 14

TLR, c-type lectins and scavenger receptors

Question 15

T/F scavenger receptors normally phagocytose non-inflammatory materials

Answer 15

T

Question 16

What deficiencies could result in chronic mucocutaneous candidasis

Answer 16

c-type lectin is really importnat in fungal immunity. Mutations and thus deficiency of Dectin 1[Dectin 1 (a c-type lectin). It binds candida. Without dectin 1 ,cannot produce IL-6 or bind], and CARD9, a protein in the downstream signalling pathays for many c-type lectins, can result in chronic mucocutaneous candidiasis.

Question 17

What is worse, dectin 1 or CARD9 deficiency

Answer 17

CARD9, because this is the signalling molecule for the actiation of many receptors