B cell activation occurs in the secondary lymphoid organs (SLOs), such as the spleen and lymph nodes. After B cells mature in the bone marrow, they migrate through the blood to SLOs, which receive a constant supply of antigen through circulating lymph. At the SLO, B cell activation begins when the B cell binds to an antigen via its BCR. Although the events taking place immediately after activation have yet to be completely determined, it is believed that B cells are activated in accordance with the kinetic segregation model , initially determined in T lymphocytes. This model denotes that before antigen stimulation, receptors diffuse through the membrane coming into contact with Lck and CD45 in equal frequency, rendering a net equilibrium of phosphorylation and non-phosphorylation. It is only when the cell comes in contact with an antigen presenting cell that the larger CD45 is displaced due to the close distance between the two membranes. This allows for net phosphorylation of the BCR and the initiation of the signal transduction pathway . Of the three B cell subsets, FO B cells preferentially undergo T cell-dependent activation while MZ B cells and B1 B cells preferentially undergo T cell-independent activation.
B cells, unlike the other two classes of lymphocytes, T cells and natural killer cells , express B cell receptors (BCRs) on their cell membrane .  BCRs allow the B cell to bind to a specific antigen , against which it will initiate an antibody response. 
Memory B cells are a B cell sub-type that are formed within germinal centers following primary infection and are important in generating an accelerated and more robust antibody-mediated immune response in the case of re-infection (also known as a secondary immune response ).  
Top 7 Foods to Lose Weight.
According to experts on nutrition, there are two types of foods that are good at helping you keep the weight off. These foods, which are fruits and vegetables, keep you full without being rich in calories. The reason why these foods keep you full for longer is that they’re rich in fiber. So if we consider fruits and vegetables as great weight loss foods, then fiber is the great weight loss nutrient.
Another nutrient that falls under this category is protein. Studies are continually showing that protein helps us curb our appetites. Protein also keeps us full for a longer time and also improves our metabolism. But remember to choose well regarding the protein you consume because as with any other kind of food, if you eat so much of it, you’ll end up gaining weight instead of losing.
These are great food choices that are sensible and low in calories. They will also help you lose more weight:
1. Green tea is one good weight loss choice. Researches say that what triggers the weight loss are the catechins found in green tea. These catechins are good phytochemicals that cause the body to burn more calories and to decrease a little of the body fat. You can enjoy green tea either hot or ice cold.
2. Soups that are broth-based or tomato-based are also good choices to have before meals because they make you less hungry and also easier to get full.
3. You will also do well by eating low-calories salads that are rich in greens. A low-calorie salad is something not filled with cheese, high-fat dressings, and croutons. These work to make you feel a lot fuller and will therefore cause you to eat less when the main course arrives. Choose the salad ingredient wisely because how much fiber it has will determine how insusceptible you will be to cravings for the rest of the day.
4. Yogurt is also another good addition. The intake of dairy products actually assists you to lose weight. A light yogurt will help you to remove hunger pangs because it has both carbohydrates and proteins.
5. Beans have a lot of protein and fiber that’s why they help keep you full. It curbs your appetite in between meals.
6. Finally, do not forget to eat whole grain cereal that is also rich in fiber. Whole grain cereals help to increase the fiber intake you get from a meal. One good way to boost up your intake of whole grain is to eat a bowl full of high-fiber whole grain cereal during breakfast or snack time.
7. Water is one of the best things you can take. Our body depends a lot on this so make sure you keep drinking it throughout the day. This beverage has no calories and you can also enjoy it as an unsweetened tea, a flavored but unsweetened mineral water, and you can also drink it regularly with just a lime or a lemon in it. Water is great for removing our toxins and it also keeps us full for longer. Whenever you feel hunger pangs coming, try to drink one glass of water before you reach for that snack.