Unit 5: Cytokines; The complement system - Practice Quiz

1 What are cytokines?

2 Cytokines produced by lymphocytes are often specifically called:

3 When a cytokine acts on the same cell that secreted it, this action is called:

4 The property of a single cytokine having many different biological effects is known as:

5 When two or more cytokines produce the same effect, this is termed:

6 Which term describes the combined effect of two cytokines being greater than the sum of their individual effects?

7 In the JAK-STAT pathway, what does the abbreviation JAK stand for?

8 In the JAK-STAT signaling pathway, STAT proteins ultimately act as:

9 What is the first event that triggers the JAK-STAT pathway?

10 JAK proteins activate STAT proteins by adding which chemical group to them?

11 The complement system is primarily a part of which type of immunity?

12 The complement system is composed mainly of:

13 Which organ is the primary site of synthesis for most complement proteins?

14 Which of the following is NOT one of the three main pathways of complement activation?

15 The classical complement pathway is typically initiated by:

16 The lectin pathway is activated by which protein recognizing carbohydrates on microbes?

17 Which complement component is central to all three activation pathways?

18 Why does the complement system require tight regulation?

19 Which regulatory protein helps protect host cells by acting as a cofactor for the inactivation of C3b?

20 The final assembled complement structure that creates pores in target cell membranes is called the:

21 A researcher observes that a single cytokine, when secreted, induces different biological effects in two different target cell types. Which property of cytokines best explains this observation?

22 A cytokine acts on the same cell that secreted it, altering that cell's own behavior. This mode of action is described as:

23 Two cytokines are administered together and produce a combined effect greater than the sum of their individual effects. This phenomenon is termed:

24 A patient's Th1 response is being suppressed by cytokines from Th2 cells. IL-10 produced by Th2 cells inhibits cytokine production by Th1 cells. This inhibitory relationship illustrates cytokine:

25 Which functional class of cytokines is chiefly responsible for directing the migration of leukocytes to sites of infection along a concentration gradient?

26 In the JAK-STAT pathway, what is the immediate event that follows cytokine binding to its receptor and receptor dimerization?

27 After STAT proteins are phosphorylated by JAKs, what enables them to bind DNA and regulate transcription?

28 A mutation abolishes SOCS (Suppressor of Cytokine Signaling) protein function. What is the most likely consequence for JAK-STAT signaling?

29 The complement system is described as a group of proteins that circulate mostly in an inactive form. What best describes how these proteins become functionally active?

30 Which liver-derived complement component is present in the highest concentration in serum and is central to all three activation pathways?

31 The classical pathway is typically initiated when C1q binds to which structure?

32 The lectin pathway is distinguished from the classical pathway primarily by its:

33 Which enzyme complex functions as the C3 convertase of the classical and lectin pathways?

34 In the alternative pathway, the C3 convertase C3bBb is stabilized against rapid decay by which protein?

35 The membrane attack complex (MAC) forms a lytic pore in target cells. Which component polymerizes to complete the transmembrane channel?

36 A deficiency in C1 inhibitor (C1-INH) leads to hereditary angioedema. This reflects that C1-INH normally functions to:

37 Patients with paroxysmal nocturnal hemoglobinuria (PNH) lack GPI-anchored regulators such as CD59 on red cells. Which consequence directly results from loss of CD59?

38 Factor I requires cofactors such as Factor H or MCP to perform which regulatory function?

39 The complement fragments C3a, C4a, and C5a are collectively known as anaphylatoxins because they:

40 Coating of a pathogen with C3b to enhance its uptake by phagocytes bearing complement receptors is an example of:

41 A cytokine binds its receptor with a in the picomolar range and exerts biological effects at concentrations far below those needed to saturate all receptors on a cell. Which property of cytokines best explains why such low occupancy can trigger a full response?

42 The terms pleiotropy and redundancy describe overlapping cytokine behaviors. Which experimental result most directly demonstrates redundancy rather than pleiotropy?

43 IL-2 receptor exists as a low-affinity ( chain alone), intermediate-affinity (), and high-affinity () form. A resting T cell expressing only chains is exposed to physiological IL-2. What is the most likely outcome?

44 A patient has a loss-of-function mutation in the common gamma chain () shared by IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21 receptors. Which downstream molecular consequence best explains the resulting X-linked SCID phenotype?

45 In the canonical JAK-STAT pathway, which sequence correctly orders the molecular events after ligand binding?

46 SOCS (suppressor of cytokine signaling) proteins provide negative feedback in JAK-STAT signaling. Which mechanism is NOT a recognized action of SOCS proteins?

47 The complement system comprises over 30 proteins. A defining feature that distinguishes complement 'activation' from constitutive presence in serum is best described as:

48 The classical, lectin, and alternative pathways converge at C3. Which statement correctly identifies the C3 convertase of each initiating pathway?

49 The alternative pathway is described as being in a state of continuous low-level activation ('tick-over'). What molecular event initiates this tick-over independent of any pathogen?

50 The lectin pathway is activated when MBL or ficolins bind carbohydrate patterns on microbes. Which pair of enzymes associated with MBL is functionally analogous to C1r and C1s of the classical pathway?

51 Formation of the C5 convertase requires addition of an extra C3b to the existing C3 convertase. Which correctly pairs the pathway with its C5 convertase?

52 Paroxysmal nocturnal hemoglobinuria (PNH) results from a somatic mutation in the PIGA gene. Why does this cause complement-mediated hemolysis of red cells?

53 Hereditary angioedema is caused by C1 inhibitor (C1-INH) deficiency. Beyond complement, why does this produce the characteristic swelling attacks?

54 Factor I is a plasma protease that cleaves C3b and C4b, but it requires cofactors. Which combination correctly matches a regulator with its principal mechanism?

55 Some pathogens, and host cells, recruit factor H using sialic acid or specific surface polysaccharides. What is the functional advantage of factor H binding for these surfaces?

56 The anaphylatoxins C3a, C4a, and C5a differ in potency. Which ranking of potency and corresponding regulatory point is correct?

57 Opsonization by C3b enhances phagocytosis. A patient with recurrent pyogenic (encapsulated bacterial) infections but intact MAC function most likely has a defect in which step?

58 A patient has recurrent, disseminated Neisseria meningitidis infections but normal responses to other bacteria and normal C3 levels. Which deficiency best explains this specific susceptibility?

59 Complement receptor CR1 (CD35) on erythrocytes plays a key role in immune complex handling. What is its principal function in this process?

60 Cytokines can act in autocrine, paracrine, and endocrine modes. Considering their typically short half-life and high receptor affinity, why is most cytokine action normally restricted to autocrine/paracrine ranges?