1. Effectively dealing with peer pressure:
The biggest reason for teens to start on drugs is due to their friends/peer groups imposing pressure on them. Hence, it is important to have a better group of friends to avoid such harmful drugs and alcohol.
2. Seeking help from parents and peers:
Help from parents and peer group should be sought immediately so that they can be guided appropriately. Help may even be sought from close and trusted friends. Getting proper advice to sort out their problems would help the young to vent their feelings of anxiety and guilt.
3. Education and counselling:
Education and counselling create a positive attitude to deal with many problems and to accept disappointments in life.
4. Looking for danger signs:
Teachers and parents need to look for a sign that indicates a tendency to go in for addiction.
5. Seeking professional and medical assistance:
Assistance is available in the form of highly qualified psychologists, psychiatrists and deaddiction and rehabilitation programmes to help individuals to overcome their problems.

Different types of antigen and antibody reactions: The reaction between soluble antigen and antibody leads to the visible precipitate formation, which is called a precipitin reaction. Antibodies that bring about precipitate formation on reacting with antigens are called as precipitins. Whenever a particulate antigen interacts with its antibody, it would result in clumping or agglutination of the particulate antigen, which is called agglutination reaction. The antibody 'involved in bringing about agglutination reaction is called agglutinin. Opsonisation or enhanced attachment is the process by which a pathogen is marked of ingestion and destruction by a phagocyte. Opsonization involves the binding of an opsonin i.e., antibody, to a receptor on the pathogens. cell membrane. After opsonin binds to the membrane, phagocytes are attracted to the pathogen. So, opsonization is a process in which pathogens are coated with a substance called an opsonin, marking the pathogen out for destruction by the immune system. This results in a much more efficient phagocytosis. The neutralization reactions are the reactions of antigen-antibody that involve the elimination of the harmful effects of bacterial exotoxins or a virus by specific antibodies. These neutralizing substances i.e. antibodies are known. as antitoxins. This specific antibody is produced by a host cell in response to a bacterial exotoxin or corresponding toxoid (inactivated toxin).

Lymph node has three zones. They are the cortex, paracortex, and medulla. The outer most layer of the lymph node is called cortex, which consists of B-lymphocytes, macrophages, and follicular dendritic cells. The paracortex zone is beneath the cortex, which is richly populated by T lymphocytes and interdigitating dendritic cells. The innermost zone is called the medulla which is sparsely populated by lymphocytes, but many of them are plasma cells, which actively secrete antibody molecules. As the lymph enters, it slowly percolates through the cortex, paracortex, and medulla, giving sufficient chance for the phagocytic cells and dendritic cells to trap the antigen brought by the lymph. The lymph leaving a node carries enriched antibodies secreted by the medullary plasma cells against the antigens that enter the lymph node. Sometimes visible swelling of lymph nodes occurs due to active immune response and increased the concentration of lymphocytes. Thus swollen lymph nodes may signal an infection. There are several groups of lymph nodes. The most frequently enlarged lymph nodes are found in the neck, under the chin, in the armpits, and in the groin.

(i) Plasmodium vivax is a digenic parasite, involving two hosts, man as the secondary host and female Anopheles mosquito as the primary host. The life cycle of Plasmodium involves three phases namely schizogony, gamogony and sporogony (f.g)
(ii) The parasite first enters the human blood stream through the bite of an infected female Anopheles mosquito. As it feeds, the mosquito injects the saliva containing the sporozites.
(iii) The sporozoites within the blood stream enter the hepatic cells of the liver and undergoes multiple asexual fission (schizogony). This produces merozoites which are released from liver cells.
(iv) The merozoites penetrate the RBC's. Inside the RBC of Blood, the merozoite of Plasmodium to develop as unicellular trophozoites. The trophozoite grows in size and a central vacuole develops pushing them to one side of cytoplasm and becomes the signet ring stage.
(v)The trophozoite nucleus then divides asexually to produce the The schizont divides and produces on nucleated merozoites.
(vi) Eventually the erythrocyte lyses, releasing the merozoites and haemozoin toxin into the blood stream to infect other erythrocytes. Lysis of red blood cells results in cycles of fever and other symptoms. This erythrocytic stage is cyclic and repeats itself approximately every 48 to72 or longer depending on the species of Plasmodium involved. The sudden release of merozoites triggers an attack on the RBCs.
(vii) Occasionally, merozoites differentiate into macrogametocytes and microgametocytes When these are ingested by a mosquito, they develop into male and female gametes respectively
In the mosquito's gut, the infected erythrocytes lyse and male and female gametes fertilize to form a diploid zygote called ookinete. The ookinete migrates to the mosquito's gut wall and develops into an oocyte.
The oocyte undergoes meiosis by a process called sporogony to form sporozoites. These sporozoites migrate to the salivary glands of the mosquito. The cycle is now completed and when the mosquito bites another human host, the sporozoites are injected and the cycle begins a new.
The pathological changes caused by malaria, affect not only the erythrocytes but also the spleen and other visceral organs. Incubation period of malaria is about 12 days. The early symptoms of malaria are headache, nausea and muscular pain. The classic symptoms first develop with the synchronized release of merozoites, hemozoin toxin and erythrocyte debris into the bloodstream resulting in malarial paroxysms - shivering chills, high fever followed by sweating. Fever and chills are caused partly by malarial toxins that induce macrophages to release tumor necrosis factor (TNF-a) and interleukin.

Protozoan Disease :
1. Protozoans are unicellular organisms and can sometimes cause illness.
2. Common protozoal diseases include malaria, giardia, and toxoplasmosis.
The two diseases caused by protozoans are Malaria and Kala-azar.
Causative agent:
1. Malaria -a single-celled parasite of the genus plasmodiu
2. Kala-azar - Leishmania organism.