干奶期预防(Prevention in the dry period)：乳房在干奶期要经过三个不同阶段，即自动退化期(Active involution)、退化稳定期(Steady state involution)和生乳期(Lactogenesis)。自动退化期是乳房自动停乳的过程，通常要30天左右，这一阶段是重新感染的最危险期，尤其是停奶后的头三周。原因是在此期间乳头部附着的菌群、乳头管内细菌的生存能力、乳头管对细菌的渗透性以及乳房内防御机能都发生了变化，有利细菌的侵入和感染。退化稳定期完全干奶，约为2周。这时乳头管收缩，乳房抗菌物质增加，细菌的渗透和生存能力降低，整个阶段临床型乳房炎极少发生。这一阶段的长短，与整个干奶期的长短呈正相关。生乳期为产犊前的大约两周，乳房发生类似第一阶段的变化，乳房内白细胞吞噬能力降低，乳房开始充乳，乳头管扩张，甚至漏奶，有利病原体的侵入，增加了感染的危险。干奶期是预防产后发生临床型乳房炎的重要时期，也是控制乳房炎发生的一个重要环节，尤其是干奶的第一、三两个阶段。有些国家已把干奶期的预防列入常规措施。干奶期预防主要是向乳房内注入长效抗菌药物，杀灭已侵入和以后侵入的病原体，有的有效期可达4～8周。
乳头管内上皮分泌的角蛋白是阻挡细菌的物理性屏障。
角蛋白内层含有抗菌剂成分，如豆蔻酸、棕榈酸、亚油酸等都属于抗菌剂。角蛋白内层与阳离子蛋白相结合，阳离子蛋白以静电方式与病原体结合，可以改变病原体细胞壁，使其对渗透压反应更敏感［3］。
在干奶期，角蛋白能完全阻塞乳导管。
程艳，刘大程，张智勇 奶牛乳房炎与乳腺免疫
朱士恩 动物生殖生理学
乳腺是一种衍生的皮肤腺，属外分泌腺，来源于外胚层。乳腺为哺乳动物独有的特殊腺体，它能够将母体的营养物质以乳汁的形式供给子代利用。虽然乳腺的数目、形状、大小及位置因动物种类不同有很大差异，但其基本结构具有共同特性。
乳腺的组织结构大体可以分为具有合成、分泌、和排乳功能的实质部分（即腺组织），以及其支持作用的间质部分。腺组织由腺泡和导管系统组成。支持组织主要由结缔组织和脂肪组织构成，其中含有血管、淋巴管、神经和韧带等组织。
腺泡由单层上皮细胞构成，细胞的形状随泌乳活动的不同时期而变化。多个腺泡聚集成群或呈小叶状。腺泡和终末乳导管相通，合成分泌的乳汁可进入导管系统。腺泡周围有一层致密的基质，内有毛细血管网。腺泡上皮细胞表面还有呈网状分布的星状的肌上皮细胞。血液中的催产素可使肌上皮细胞收缩，从而使腺泡腔内德乳汁进入导管，进而从乳头管输出。
乳腺腺泡相连着导管系统中最细小的终末乳导管，再逐渐汇集形成乳导管和较大的乳导管，最后通到乳腺乳池或乳头的末端。终末乳导管的管壁也由单层上皮细胞构成，并有泌乳功能，细胞表面也有肌上皮细胞，与腺泡一样受血液中催产素的支配。
除有袋类的雄性没有乳腺外，乳腺一般在哺乳动物的雌雄两性中都存在，但雄性乳腺常常发育不良，但只有雌性动物的乳腺能够在出生后在动物相关激素的作用下逐渐发育为具有泌乳功能的成熟乳腺。从出生到乳腺发育完全，乳腺形状和功能经历着幼年期到初情期转变。此后，乳腺在生殖周期的循环中经历着腺体发育，泌乳的发动，泌乳的维持和腺体的退化，其间，乳腺的形状、功能和生理状态在生理水平调控下发生改变并产生适应性变化，例如：大小，乳汁的合成，激素水平，免疫力强度等。
泌乳高峰期后，乳腺会发生退行性的变化及乳腺的回缩。距离乳腺乳池远端的腺泡最早开始退化，体积变小，腺泡腔消失，细胞以自溶方式解体；终末乳导管萎缩；腺小叶也退化成只有少数分支的小管；腺组织逐渐被脂肪组织和结缔组织所代替。由于乳房的一系列变化不仅使体积变小，泌乳量也大大减小，最后泌乳活动停止而进入干乳期。乳腺回缩时，会有大量巨噬细胞浸润至乳腺内，因而在乳腺完全回缩后，淋巴细胞就成了腺体内数量较多的细胞。
奶牛泌乳早期如若停止哺乳或挤奶，乳腺回缩的速度会增快。由于乳汁积聚在腺泡腔和导管系统内不能排出，使乳腺细胞的代谢活动迅速降低，退化速度加快。同时，腺泡内压大于血压，使血液循环受阻，乳成分的前体物也无法进入分泌细胞内，影响了乳的合成。堆积的乳汁逐渐被吸收，腺泡最终萎缩和崩解。
性周期短的大鼠在泌乳之后全部小叶腺泡系统即行消失，而性周期长的动物由于有功能黄体期，能保留部分腺泡。干乳期中，动物原有的乳腺组织会所退化，为适应再一次的泌乳期的到来，又会重新形成新的乳腺组织，这就是乳腺的改建过程。因而，泌乳期之间的干乳期对于能否在下一个泌乳期获得高水平的产乳量十分重要。经过几个干乳期后，乳牛的乳腺可改建到发育最好的阶段，也使产乳量达到一生中的高产期。随着年龄的增大，每次干乳期的改建程度会减弱，泌乳量也就逐年减少。
巢国正等应用改良甲苯胺蓝染色法(MTB)观察了大鼠泌乳期和静止期乳腺肥大细胞的分布、形态、数量变化规律．并用阿尔新蓝一番红鉴别染色法(AB—S)进行了细胞化学分型研究，发现大鼠乳腺只存在黏膜型肥大细胞
乳腺虽是哺乳动物特有的皮肤腺，但从其免疫学本质来看，乳腺属于黏膜免疫器官【12，13】
我们对其他动物的研究中也发现，奶牛乳腺只有黏膜型肥大细胞【9】[9] 王家鑫，陈耀星，赵香汝，等．奶牛乳腺肥大l细胞的黏膜免疫学特征[J]．上海免疫学杂志，2001，21(3)：140—143．
众所周知，乳腺和子宫有共同的特性，即其结构在不同生理时期可发生很大的变化，而且这种变化受生殖激素的调节。
这也提示，乳腺局部免疫接受内分泌激素的调节
大鼠乳腺局部免疫的调节机制中国兽医学报2005年1月 第25卷第1期
但有一种观点认为，在乳腺的天然免疫中，乳头管的括约肌构成了阻止病原微生物入侵的第一道防线，是主要的天然免疫屏障。随着仔鼠的吮乳和断乳后乳腺的萎缩，致使乳头管括约肌松弛，各种病原微生物极易进入乳腺组织，易发生乳腺炎【18】
[18] Galli S J．New concepts about the mast cell[J]．N Engl J Med，1993，328(4)：257—265．
乳房炎(mastitis)是一种在奶牛业中多发的极其复杂的疾病,特别是亚临床乳房炎,尽管有多年的研究,但乳房炎仍然是奶牛群中花费最多的疾病。畜群调查结果表明美国30%~70%的母牛至少有一个被感染的乳区,乳房炎被列为母牛淘汰的主要原因,每年用于母牛乳房炎的花费是182美元/头,淘汰乳用乳牛的26.5%,都是因为患乳房炎之故。法国整个第一乳期临床乳房炎发生率为26.3%。在芬兰、挪威、瑞典,因乳房健康问题而淘汰的母牛分别占总淘汰母牛的35%、19%和22%。
谢光美,赖松家 CXCR2基因与奶牛乳房炎中国畜牧兽医 2006年3月第一期
Cytokines produced during urinary tract infection induced by Escherichia coli challenge include tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6, and IL-8 (2, 15, 37), while another study showed local production of these cytokines during experimental Actinobacillus pleuropneumoniae infection of the lung (4).埃希氏菌属诱导产生的尿道感染期间产生的细胞因子包括肿瘤坏死因子（TNF），IL-1、IL-6和IL-8（2、15、37），而另一个研究显示肺部感染胸膜肺炎放线杆菌使局部产生这些细胞因子。
One of these studies also showed a close temporal correlation between IL-8
production and the number of neutrophils migrating to the site of infection (2).这些研究也显示IL-8的生成和是中性粒细胞迁移进入感染部位之间存在紧密短暂的相关。
Thus, it is clear that cytokines capable of recruiting host defenses are produced in abundance during infection at an epithelial surface.
这样很明显，在上皮感染时，能招募宿主免疫的细胞因子大量产生。
Furthermore, clinical mastitis caused by intramammary infection with coliform bacteria, including E. coli, is common among dairy cows on commercial farms because the mammary gland is susceptible to infection with E. coli from the cow’s environment (8, 19).此外，乳房内感染大肠杆菌引起的临床型乳房炎在商业牧场中乳用奶牛上是普遍的，因为乳腺易感环境中的大肠杆菌。
Local production of inflammatory mediators during intramammary infection is consistent with studies of mucosal infection, where local production of TNF,
IL-1, IL-6, IL-8 and other cytokines was found during E. coli urinary tract infection (2, 15, 37) and pleuropneumonia caused by the gram-negative bacterium Actinobacillus pleuropneumoniae (4).乳房内感染期间，炎性介质的局部产生与黏膜感染的研究结果一致，如：大肠杆菌泌尿道感染发现的TNF,IL-1, IL-6, IL-8和其它细胞因子（2.15.37）
These earlier studies were able to demonstrate TNF production only by quantitation of mRNA levels, because TNF bioactivity was undetectable in inflammatory fluid. During our study of intramammary infection with E. coli, TNF bioactivity was found in milk, but only among glands with severe infections and only for a short period during the onset of inflammation.
这些早期研究能证明TNF仅能在mRNA水平定量，因为炎性液体中不能检测到TNF生物活性。在我们的大肠杆菌乳房内感染中，TNF生物活性在乳中发现，但是仅感染严重的腺体和炎症的起始阶段短暂出现。
Low concentrations of inflammatory mediators or their activity were sometimes found in milk before challenge or in the milk of uninfected glands. Although some of this activity may have been nonspecific, other investigators have also noted low concentrations of TNF, IL-6, and IL-8 in secretions of noninflamed mammary glands or unstimulated mammary epithelial cultures (5, 34, 46).在挑战之前或未感染乳腺所产乳中有时低浓度的炎性介质及其低生物活性。尽管这些活性可能是非特异性的，其他研究人员在非炎性乳腺和非处理乳腺上皮下培养物中也注意到低浓度的TNF, IL-6, and IL-8（5，34.36）。
The physiological significance of basal levels of these mediators is unknown. Although they do not induce obvious inflammation, these mediators may contribute to the small influx of leukocytes that occurs even in uninfected glands, particularly during physiological transitions of the mammary gland (34).这些介质的基础水平的生理重要性仍然未知，尽管它们不引起明显炎症，这些介质可能有助于未感染腺体内出现的白细胞少量流入，尤其是乳腺生理性转运。（34）。
Neither C5a, IL-8, nor LTB4 was able to induce more than a small neutrophil influx when infused alone into the bovine teat cistern, whereas endotoxin,
IL-1, and TNF induced strong responses (29). Thus, these chemoattractants probably do not act alone in the recruitment of neutrophils to an infected epithelial surface.当单独注入乳头管时，C5a，IL-8都不能引起更多的嗜中性粒细胞流入，而内毒素、IL-1和 TNF能引发强烈反应。（29）这样，这些趋化因子可能在招募嗜中性粒细胞进入感染上皮过程中不能单独起作用。
Production of complement fragment C5a, tumor necrosis factor, and interleukin-1 (IL-1) occurred earlier than production of IL-6 or IL-8.
补体片段C5a，肿瘤坏死因子和IL-1出现的比IL-6和IL-8早。
Complement Fragment C5a and Inflammatory Cytokines in Neutrophil Recruitment during Intramammary Infection with Escherichia coli
DALE E. SHUSTER,1* MARCUS E. KEHRLI, JR.,1 PASCAL RAINARD,2
INFECTION AND IMMUNITY, Aug. 1997, p. 3286–3292 Vol. 65, No. 8
Proteins and other molecules are sufficient to kill microbes that have not yet been engulfed by cells (Beutler, 2004). Complement, lysozyme, lactoferrin, and antimicrobial peptides are among the proteins most commonly cited in this regard (Gru¨ n, 1985; Malinowski, 2002; Schmitz et al., 2004). There is no doubt that several innate immune proteins provide a measure of protection in the mammary gland cisterns. However, in the bovine udder the protective role of some of them seem to be unimportant (e.g., lysozyme). Furthermore, some of them have actions that depend on the stage of the lactation cycle (e.g., lactoferrin is only effective during steady-state involution in the absence of citrate; Smith and Schanbacher, 1977; Rejman et al., 1989).蛋白和其它分子足以能杀死这些还没有被细胞吞噬的微生物(Beutler, 2004)，补体，溶菌酶，乳铁蛋白和抗菌肽是这些蛋白当中最常提到的(Gru¨ n, 1985; Malinowski, 2002; Schmitz et al., 2004).。毫无疑问，多种固有免疫蛋白位于乳池中提供保护。但是，牛乳房中，这些保护中的一些看似并不重要，（如溶菌酶），此外，其中一些保护发挥作用还依赖于泌乳循环阶段（如乳铁蛋白仅在缺乏柠檬酸盐的退化稳定期具有作用，Smith and Schanbacher, 1977; Rejman et al., 1989）。
Lactoferrin, the major protein found in mammary secretions during steady-state involution, reaches very high concentrations (Smith and Schanbacher, 1977; Rejman et al., 1989). The mechanism of lactoferrin activity has not been clearly defined but appears to originate primarily through sequestration of iron necessary for bacterial growth or through direct interaction of its ationic N-terminal region with bacterial components
or both. Among the mastitis pathogens, E. coli are the most susceptible, followed by Staphylococcus aureus. treptococci seem to be resistant (Rainard, 1986a). The citrate:lactoferrin ratio is lowered (because milk synthesis as stopped) and immunoglobulin concentrations reelevated. The bacteriostatic activity of lactoferrin can be enhanced by antibodies specific to mastitis- ausing bacteria, possibly by interfering with the acterial iron-acquisition systems (Rainard, 1986b; Oliver nd Bushe, 1987).乳铁蛋白，是一种退化稳定期乳腺分泌物中发现的主要蛋白，并且具有很高的浓度（Smith and Schanbacher, 1977; Rejman et al., 1989）。乳铁蛋白作用机制仍不清楚，但是作用的发挥可能主要通过剥夺细菌生长所必须的铁离子或通过其N-端阳离子和细菌组分的相互作用，或者两者途径都有。乳腺炎病原体中，大肠杆菌是最具易感性，金黄色葡萄球菌次之，链球菌似乎具有抵抗性(Rainard, 1986a)，柠檬酸盐与乳铁蛋白的比例降低（因为乳汁合成停止），并且免疫球蛋白浓度再次升高。乳铁蛋白的抑菌活性可被增强通过抗体特异性需铁系统(Rainard, 1986b; Oliver nd Bushe, 1987).。
Lipopolysaccharide-binding protein is a hepatocyte-derived cute phase protein, the expression of which is up-regulated by IL-1 and IL-6 (Tobias et al., 1999; Schumann nd Latz, 2000).
脂多糖结合蛋白是一种肝细胞急性期蛋白，其IL-1 和 IL-6能使其表达上调(Tobias et al., 1999; Schumann nd Latz, 2000).。
Lysozyme is one of the most important antibacterial factors in milk, because it hydrolyzes the glycosidic β-(1-4) linkage between Nacetylmuramic acid and N-acetylglucosamine of the peptidoglycan polymer in the bacterial cell wall (Imoto et al., 1972).溶菌酶是乳中重要的抗菌成分之一，因为它水解细菌细胞壁上的肽聚糖多聚体的N-乙酰葡糖氨酸和Nacetylmuramic acid之间的配糖基b-(1-4)糖苷键(Imoto et al., 1972).。Imoto, T., L. N. Johnson, A. T. C. North, D. C. Philips, and J. A. Rupley. 1972. Vertebrate lysozyme. Pages 665–868 in The Enzyme. Vol. 7. P. D. Boyer, ed. Academic Press, New York, NY.
The lysozyme content and its physicochemical and enzymatic properties vary widely in the milk of different species. Human and equine milks are very rich in lysozyme (Chandan et al., 1964; Jauregui-Adell, 1975), whereas the milk of many other species contains low concentrations (Chandan et al., 1965; McKenzie and White, 1986; Elagamy et al., 1996). 不同物种的溶菌酶含量和其物理化学以及酶特性具有很大差异。人和马乳中富含溶菌酶(Chandan et al., 1964; Jauregui-Adell, 1975)，Chandan, R. C., K. M. Shahani, and R. G. Holly. 1964. Lysozyme content of human milk. Nature 204:76–77. Jauregui-Adell, J. 1975. Heat stability and reactivation of mare milk lysozyme. J. Dairy Sci. 58:835–838.而其他多种物种乳中仅含低浓度溶菌酶(Chandan et al., 1965; McKenzie and White, 1986; Elagamy et al., 1996)。Chandan, R. C., R. M. Parry, and K. M. Shahani. 1965. Purification and some properties of bovine milk lysozyme. Biochim. Biophys. Acta 110:389–398. McKenzie, H. A., and F. H. White, Jr. 1986. Determination of lysozyme activity at low levels with emphasis on the milk enzyme. Anal. Biochem. 157:367–374. Elagamy, E. I., R. Ruppanner, A. Ismail, C. P. Champagne, and R. Assaf. 1996. Purification and characterization of lactoferrin, lactoperoxidase, lysozyme and immunoglobulins from camel’s milk. Int. Dairy J. 6:129–145.
Among various species, the specific activities of lysozyme also differ because they possess different charges. Human milk lysozyme has about 3 times more lytic activity than that of egg white lysozyme because it possesses a greater positive charge than the latter (Parry et al., 1969). 在不同物种之间，溶菌酶的特意活性也有很大不同，因为它们担负着不同的作用。人乳汁中溶菌酶的水解活性是蛋清中溶菌酶活性的3倍，因为它比后者带了更大的正电荷(Parry et al., 1969)。Parry, R. M., R. C. Chandan, and K. M. Shahani. 1969. Isolation and characterization of human milk lysozyme. Arch. Biochem. Biophys. 130:59–65.
Bovine (Chandan et al., 1965) and horse (Bell et al., 1981) milk lysozymes possess even less positive charge than egg white lysozyme and also have less lytic activity. The specific activity of human milk lysozyme is about 10 times greater than that of bovine lysozyme. Therefore, human milk lysozyme plays an important role in host defenses. 牛奶(Chandan et al., 1965) Chandan, R. C., R. M. Parry, and K. M. Shahani. 1965. Purification
and some properties of bovine milk lysozyme. Biochim. Biophys.
Acta 110:389–398.和马奶(Bell et al., 1981) Bell, K., H. A. McKenzie, V. Muller, C. Rogers, and D. C. Shaw. 1981. Equine whey proteins. Comp. Biochem. Physiol. 68B:225–236.溶菌酶比蛋清中溶菌酶带了更少的电荷，且其水解活性更差。人乳溶菌酶特异活性是牛乳菌酶活性的10倍。因此，人乳溶菌酶在机体防御中起着更重要的作用。
In human milk, the role of lysozyme in reducing microbial infections in the gastrointestinal tract of breast-fed infants has been extensively studied (Lo¨nnerdal, 1985). Most gram-positive bacteria and a few gram-negative bacteria are damaged by human milk lysozyme, which helps to increase the levels of beneficial microorganisms in infants and strengthen their disease resistance.人乳汁中，溶菌酶减少母乳喂养的新生儿胃肠道微生物感染的作用已被广泛的研究(Lo¨nnerdal, 1985)。Lo¨nnerdal, B. 1985. Biochemistry and physiological function of human
milk proteins. Am. J. Clin. Nutr. 42:1299–1317.大多数革兰氏阳性菌和一些革兰氏阴性菌能被人乳汁溶菌酶破坏，这有助与增加婴儿有益微生物的水平和增强他们的疾病抵抗力。
When lysozyme was added to infant formula, formula-fed infants showed reduced incidences of gastroenteritis and allergies and an increase in beneficial microflora in the gastrointestinal tract (Francis, 1980). 当溶菌酶被添加进婴儿配方时，
The Food and Agriculture Organization/World Health Organization and many countries such as Australia, Belgium, Denmark, Finland, France, Germany, Italy, Japan, Spain, and the United Kingdom have acknowledged the nontoxicity of lysozyme and have approved its use in some foods and in pharmacological 2912 YU ET AL. and therapeutic applications (Cunningham et al., 1991). However, because the source of human lysozyme is limited, research identifying recombinant sources of human lysozyme could be very beneficial. The first research on transgenic mice expressing human lysozyme was conducted by Maga et al. (1994).
J. Dairy Sci. 89:2911–2918
. American Dairy Science Association, 2006.
Expression and Bioactivity of Recombinant Human Lysozyme in the Milk of Transgenic Mice
Z. Yu, Q. Meng, H. Yu, B. Fan, S. Yu, J. Fei, L. Wang, Y. Dai, and N. Li1
