2/14/12

StudyBlue printing of 2/14/12 html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, font, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td { margin: 0; padding: 0; border: 0; outline: 0; font-size: 100%; background: transparent; } body { line-height: 1; } blockquote, q { quotes: none; } blockquote:before, blockquote:after, q:before, q:after { content: ''; content: none; } /* remember to define focus styles! */ :focus { outline: 0; } /* remember to highlight inserts somehow! */ ins { text-decoration: none; } del { text-decoration: line-through; } /* tables still need 'cellspacing="0"' in the markup */ table { border-collapse: collapse; border-spacing: 0; } /* end RESET */ .header { min-width:800px; } .logo { padding:6px 20px 2px 20px; margin:0; font-size:25px; font-weight:bold; color:#808285; position:relative; border-bottom: 1px solid #c5c5c5; } .logo-blue { color:#70adc4; } .logo-desc { font-weight:normal; font-size:19px; color:#cccccc; margin-top:50px; position:absolute; display: none; } .back-button { position:absolute; top:20px; right:20px; font-size:13px; line-height:25px; color:rgb(0,175,225); font-weight:normal; } .back-button a { color:rgb(0,175,225); } .instructions { padding:0; margin:0; width:100%; position:relative; color:rgb(100,100,100); } .step-holder { border-left:1px solid #ededed; margin-left:20px; } .steps { padding:15px 0; float:left; width:24%; border-right:1px solid #ededed; text-align:center; } .steps-01 { } .steps-02 { } .steps-03 { } .steps-04 { } .label { padding:5px 10px; } .print-button { } .print-button a { background-color:rgb(0,175,225); color:white; line-height: 19px; padding:9px 8px 5px 30px; font-size:14px; text-decoration:none; background-image: url(images/printer.png); background-repeat: no-repeat; background-position: 7px 50%; -moz-border-radius: 5px; -webkit-border-radius: 5px; } .print-button a:hover { background-color:black; } .theNote .content { width: 8.0in !important; margin: 5px auto; padding:20px; background-color:white; } .theNote .header { border-bottom: 1px dashed #C8C8C8; font-size: 17px; padding: 0 0 10px; line-height: 19px; color: #00ADE1; min-width:500px; } .theNote .body { font-size: 14px; line-height: 19px; padding: 10px 0; } .theNote{ padding:6px 0; clear:both; background-color: rgb(200,200,200); } .theNote h3{ color: rgb(100,100,100); } .theNote h1, .theNote h3{ background-color:white; padding:2px 20px; width:8.0in !important; margin: 0 auto; font-size: 15px; } .theNote h1{ padding-top: 10px; font-size: 15px; } .theNote h1:first-child{ font-size: 20px; } .theNote h3 { font-size: 14px; font-weight: normal; } #options { border: 3px double #ccc; padding: 5px 12px; margin: 10px 50px 10px 20px; float: left; } #info { border-top: 1px solid #ccc; padding-top: 5px; font-style: italic; } li { margin: 5px 10px 5px 25px; } ul li { list-style: disc; } ol li { list-style: decimal; } img { border: 0; } table { clear: both; width: 100%; border: 1px solid #c5c5c5; border-width: 1px 0; margin: 0; page-break-after: always; } table#page { page-break-after: auto; } td { text-align: center; font-size: 12px; border-bottom: 1px dashed #c5c5c5; height: 1.75in; width: 50%; padding-left: 15px; } .leftside { border-right: 1px solid #cccccc; padding: 0 15px 0 0; } .bottom td { border-bottom: none; } .clearfix { clear:both; line-height:1px; height:1px; } img { max-width:80%; max-height:150px; margin:20px; } @media print {.header { display: none; } .content .header{ display:inherit; } table { border: 1px dashed #bbb; border-width: 1px 0; } .theNote{ background-color:white; } } 2/14/12 How do we get IgM and IgD expressed on the same mature B cell? example of alternative splicing mu and delta genes close and adjacent to one another splicing at different poly-A sites results in either only mu exons or both mu and delta exons, in which case the mu exons will be spliced out What is the role of IgM and/or IgD on B cells? sign of an antigen-competent (mature) B cell may be involved in helping determine whether or not we are going to recognize self anergic B cell - unable to respond -- migrates to periphery after not seeing enough antigen in its development IgM and IgD that self-react trigger apoptosis What other mechanisms can contribute to diversity in Ig specificity? somatic mutation - occurs in periphery after interaction w/ antigen mutations are predominantly found in the CDRs initial contant involves primarily IgM after about 14 days of exposure IgG becomes involved and mutations pile up in CDRs after about 21 days a class switch has occurred, and IgG predominates - more mutations in hypervariable regions How does somatic mutation lead to increased antibody affinity? affinity maturation when antibodies outnumber antigen present, Ab's w/ higher affinity are the only ones that bind to antigen and are selected for - B cell clones with less affinity stop secreting antibody ability to adapt better fitting antibodies continues to increase through subsequent responses situations in which we encounter antigens for which we have no antibodies ---> epidemics independent of what is occurring at idiotype --- class switching is also happening how do you determine whether or not a B cell is a memory cell? >>> may have other Ig's on its surface, such as IgG or IgA B cells recognize antigen as immune complexes bound to the surface of follicular dendritic cells -- allow B cells to see soluble antigen -- important in nurturing development of B cells Immune complexes bound to follicular dendritic cells form iccosomes, which are released and can be taken up by B cells in the germinal center. -- Not completely necessary but enhances resopnse How do we get isotype switching? cytokine stimulates the change repetitive DNA sequences that guide isotype switching are found upstream of each of the Ig C-region genes, with the exception of the delta gene. switching occurs by recombination b/t these repetitive sequences enzymes cleave out unneeded loops - looping out splicing at switch regions can you express IgM on a B cell after it has "switched" to secreting IgG? No --> any B cell that has undergone an isotype switch will no longer be able to express the isotypes that it has spliced out --> at cellular level