Test 1 key - Key to Bio360K test 1 1. How does defensin...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Sheet1 Page 1 Key to Bio360K test 1 1. How does defensin kill bacteria? (3) Defensin damages bacterial membrane. Which cell type(s) produces defensin? (3) Epithelial cells and neutrophils 2. What is the function of secretory IgA? (4) Secretory IgA binds to pathogens and toxins on mucosal surface and excludes them from the body. During transcytosis, sIgA transports antigens from the basal to the apical surface of mucosal epithelial cells. This function serves to eliminate potentially harmful antigens from the body. Moreover, the transit process may allow sIgA to intercept infecting virus in the endosomal pathways. Can IgG substitute for the function of secretory IgA? Why? (3) No. 1) IgG is not transported across the mucosal epithelial cells. 2) IgG can activate complements and macrophages through Fc.Rs. These reactions are inflammatory and may harm mucosal tissues. By contrast, sIgA does not engage complements and FcaR, and is not inflammatory. 3) sIgA is dimeric, whereas IgG is monomeric. For this reason, sIgA is more effective than IgG at aggregating antigens and prevents the interaction of pathogens with host tissues. 3. Which class(s) of antibody activates complements? (3) IgM > IgG1, IgG3 > IgG2 There are abundant antibodies in blood circulation. Do these antibodies activate complements in the absence of infection? Why? (3) No. Antibodies only activate complements in the context of immune complexes. The binding site for C1q is located in the Fc region of antibodies. This binding site is only revealed under the condition of antibody-antigen complex. 4. There are multiple mechanisms to avoid complement damage to host cells. Please give an example. (3) During complement activation, C3 may be attached to host cell surface and form the alternative C3 convertase C3bBb. The complex can be inactivated by factor H or CR1 on host cells. These regulatory proteins displace Bb from C3b and recruit factor I to cleave C3b into inactive fragments. 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

Test 1 key - Key to Bio360K test 1 1. How does defensin...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online