**2.1 Kupffer cells**

Kupffer cells are the macrophages that reside in liver and are the highest number of resident macrophages in body. Kupffer cells are basically phagocytes that remove pathogens that in the circulation. Their presence in hepatic sinusoids allows them to perform the above said function efficiently. They also act against substances which are immunoreactive that enter through the portal circulation from the gastrointestinal tract. As Kupffer cells act against immunoreactive substances that enter from the GIT to portal circulation so they can be regarded as a barrier in the gut. It inhibits many inflammation that may occur due to these immunoreactive substances by destroying them in hepatic sinusoids. The Kupffer cell also plays a major role in clearing the dead red blood cells and comprise the mononuclear phagocytic system due to its phagocytic activity. Though Kupffer cells plays a major role in in protecting the liver from injuries due to alcohol, drugs or toxins, however their

**Figure 1.** *Hepatocyte ultrastructure [3].*


**Table 1.**

*Hepatic cell type and their functions [4].*

inflammatory response leads to conditions like chronic inflammation in liver which may be due alcoholic as well as non-alcoholic liver disease [5].

## **2.2 Hepatic sinusoids**

The hepatic sinusoids are covered by specific endothelial cells that leads to formation of a barrier, which is porous in nature, that aid in exchange of materials among the hepatocytes and blood. The endothelial cells helps the clusters of differentiation markers such as CD14, CD16, CDw32, CD36, CD54, CD13 and CD4. They possess specific phenotype for portal venules, capillary endothelium, and terminal hepatic venule. It can be seen that the endothelium of portal tract arterioles, branches of portal vein and central veins binds with *U. europaeus* lectin and eventually stains CD34 and CD31 positively [6]. However sinusoidal endothelium in the majority of lobules are generally negative for CD34 and laminin. Positive staining of sinusoids is seen with carcinoma of hepatic cells as they stain sinusoid like vessels [7, 8]. Sinusoidal lumen contains cells such as kupffer cells, macrophages which can be seen by immunostain for CD68. Activated kupffer cells are positive with DPAS and muramidase [9, 10].

### **2.3 Hepatic stellate cells**

Hepatic stellate cells belong to the family of myofibroblasts. Stellate cells show their activity in the process of fibrogenesis and regulate flow of sinusoidal blood [11, 12]. They play the role of antigen presenting cells as well. Stellate cells during the childhood or adolescence phases are positive for actin whereas they are negative in adults and become positive only when there is any pathological condition [13]. Whereas in the case of synaptophysin, which is one of the main synaptic vesicle protein p38 and is encoded by the SYP gene, activated as well as resting stellate cells are positive. Stellate cells normally cannot be seen in a healthy liver whereas in pathological conditions they can be identified by vacuolated cytoplasm and a nucleus that becomes scalloped. Hepatic stellate cells are also related to the synthesis of collagen [14, 15].
