抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Long-term potentiation of synaptic transmission in the hippocampus is the primary experimental model for investigating the synaptic basis of learning and memory in vertebrates. The best understood form of long-term potentiation is induced by the activation of the N-methyl-D-aspartate receptor complex. This subtype of glutamate receptor endows long-term potentiation with Hebbian characteristics, and allows electrical events at the postsynaptic membrane to be transduced into chemical signals which, in turn, are thought to activate both pre- and postsynaptic mechanisms to generate a persistent increase in synaptic strength.

A synaptic model of memory: long-term potentiation in the hippocampus

Simple Combinations of Lineage-Determining Transcription Factors Prime cis-Regulatory Elements Required for Macrophage and B Cell Identities

The selective degradation of many short-lived proteins in eukaryotic cells is carried out by the ubiquitin system. In this pathway, proteins are targeted for degradation by covalent ligation to ubiquitin, a highly conserved small protein. Ubiquitin-mediated degradation of regulatory proteins plays important roles in the control of numerous processes, including cell-cycle progression, signal transduction, transcriptional regulation, receptor down-regulation, and endocytosis. The ubiquitin system has been implicated in the immune response, development, and programmed cell death. Abnormalities in ubiquitin-mediated processes have been shown to cause pathological conditions, including malignant transformation. In this review we discuss recent information on functions and mechanisms of the ubiquitin system. Since the selectivity of protein degradation is determined mainly at the stage of ligation to ubiquitin, special attention is focused on what we know, and would like to know, about the mode of action of ubiquitin-protein ligation systems and about signals in proteins recognized by these systems.

The Ubiquitin System

Rapid progress in deciphering the biological mechanism of Alzheimer's disease (AD) has arisen from the application of molecular and cell biology to this complex disorder of the limbic and association cortices. In turn, new insights into fundamental aspects of protein biology have resulted from research on the disease. This beneficial interplay between basic and applied cell biology is well illustrated by advances in understanding the genotype-to-phenotype relationships of familial Alzheimer's disease. All four genes definitively linked to inherited forms of the disease to date have been shown to increase the production and/or deposition of amyloid β-protein in the brain. In particular, evidence that the presenilin proteins, mutations in which cause the most aggressive form of inherited AD, lead to altered intramembranous cleavage of the β-amyloid precursor protein by the protease called γ-secretase has spurred progress toward novel therapeutics. The finding that presenilin itself may be the long-sought γ-...

Alzheimer's Disease: Genes, Proteins, and Therapy

In the genome of a germ-line cell, the genetic information for an immunoglobulin polypeptide chain is contained in multiple gene segments scattered along a chromosome. During the development of bone marrow-derived lymphocytes, these gene segments are assembled by recombination which leads to the formation of a complete gene. In addition, mutations are somatically introduced at a high rate into the amino-terminal region. Both somatic recombination and mutation contribute greatly to an increase in the diversity of antibody synthesized by a single organism.

Somatic generation of antibody diversity

RAG-1-deficient mice have no mature B and T lymphocytes

http://www.columbia.edu/itc/hs/medical/neuralsci/2003/slides/34_GeneticSlides.pdf

The Essential Role of Hippocampal CA1 NMDA Receptor–Dependent Synaptic Plasticity in Spatial Memory

Publisher Summary
This chapter reviews the somatic generation of antibody diversity. It was shown that a typical antibody molecule is composed of two identical light chains and two identical heavy chains. It had also been found that each of these two types of chain exhibits great sequence variability in the amino terminal region between one antibody molecule and the next and no sequence variability in the carboxyl terminal regions. Use of restriction enzymes and recombinant DNA methods allowed resolution of a long-standing and central issue in immunology, the genetic origins of antibody diversity. It turned out that an organism does not inherit even a single complete gene for antibody polypeptide chains. Rather, the genetic information is transmitted in germline as no more than several hundred gene segments. Through a series of specialized somatic recombination occurring specifically during the differentiation of B lymphocytes, these gene segments are assembled into tens of thousands of complete genes. In the immune system, organisms have exploited two major processes for modification of DNA, recombination and mutation, as a means to diversify somatically the limited amount of inherited genetic information to cope with the vastly diverse antigen universe. Somatic diversification allows the individual organism to generate a virtually limitless number of lymphocyte variants.

Somatic Generation of Antibody Diversity1

As a first step in a program to use genetically altered mice in the study of memory mechanisms, mutant mice were produced that do not express the alpha-calcium-calmodulin-dependent kinase II (alpha-CaMKII). The alpha-CaMKII is highly enriched in postsynaptic densities of hippocampus and neocortex and may be involved in the regulation of long-term potentiation (LTP). Such mutant mice exhibited mostly normal behaviors and presented no obvious neuroanatomical defects. Whole cell recordings reveal that postsynaptic mechanisms, including N-methyl-D-aspartate (NMDA) receptor function, are intact. Despite normal postsynaptic mechanisms, these mice are deficient in their ability to produce LTP and are therefore a suitable model for studying the relation between LTP and learning processes.

https://science.sciencemag.org/content/sci/257/5067/201.full.pdf

Susumu Tonegawa

Papers

Somatic generation of antibody diversity

RAG-1-deficient mice have no mature B and T lymphocytes

The Essential Role of Hippocampal CA1 NMDA Receptor–Dependent Synaptic Plasticity in Spatial Memory

Somatic Generation of Antibody Diversity1

Deficient Hippocampal Long-Term Potentiation in α-Calcium-Calmodulin Kinase II Mutant Mice