Overview:
SMADs are essential intracellular components for the signal transduction of TGFβ family members. SMAD2 is an intracellular mediator of TGFβ family and activin type 1 receptor (1). SMAD2 mediate TGFβ signaling to regulate cell growth and differentiation. SMAD2 is released from cytoplasmic retention by TGFβ receptor-mediated phosphorylation. The phosphorylated SMAD2 then forms a heterodimeric complex with SMAD4, and this complex translocates from cytoplasm into nucleus. By interacting with DNA-binding proteins, SMAD2 complexes then positively or negatively regulate the transcription of target genes. Inactivating mutations in SMAD2 have been found in various cancers (2).
Gene Aliases:
JV18, MADH2, MADR2, JV18-1, hMAD-2, hSMAD2, MGC22139, MGC34440
Genbank Number:
NM_001003652
References:
1.Masayuki, F. et al: Identification and Characterization of Constitutively Active Smad2 Mutants: Evaluation of Formation of Smad Complex and Subcellular Distribution. Molecular Endocrinol. 2000; 14 (10): 1583-1591.2.Eppert, K. et al: MADR2 maps to 18q21 and encodes a TGF-beta-regulated MAD-related protein that is functionally mutated in colorectal carcinoma. Cell. 1996; 86: 543-552.
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所以一个细菌或病毒可以有很多的抗原。
若已进入细胞内。则先由巨噬细胞吞噬降解。并形成抗原-MHC复合体传送到表面。被辅助性T淋巴细胞识别和效应T淋巴细胞识别后。效应T淋巴细胞被激活。分解靶细胞。然后再由效应B细胞分泌的抗体进一步消灭病毒。
还有不清楚的么？
荚膜（capsule）是某些细菌在生长繁殖过程中分泌的一层黏液性物质，包围在细胞壁外，通常这种黏液层厚度小于0.2μm，成分是多糖或多肽，只有在营养丰富时或在动物体内，细菌才产生这种半抗原性质的黏液性物质。它具有保护菌体免受巨噬细胞等的捕捉和吞噬，因而具有抗吞噬抗消化、侵袭力强、与致病性关系密切等特点。像肺炎球菌、炭疽杆菌等都有这类荚膜。有些细菌的荚膜层较薄，小于0.2μm，称为微荚。
像链球菌的M蛋白、伤寒杆菌的Vi抗原、大肠杆菌的K抗原等都属于这类微荚膜。
请赐教！
