Lymphocytes and Immunity
A lymphocyte is a type of white blood cell in the vertebrate immune system.There are two broad categories of lymphocytes, namely the large granular lymphocytes and the small lymphocytes depending on their appearance under microscope.
Most, but not all large granular lymphocytes are more commonly known as the natural killer cells (NK cells). The small lymphocytes are the T cells and B cells. Lymphocytes play an important and integral role in the body’s defenses
NK cells are a part of innate immune system and play a major role in defending the host from both tumors and virally infected cells. NK cells distinguish infected cells and tumours from normal and uninfected cells by recognizing alterations in levels of a surface molecule called MHC (major histocompatibility complex) class I. Read more
Active and Passive Immunity
6. Acquired immune (adaptive/specific) responses can be active or passive. Describe and differentiate the two.
Both are types of acquired immunity..
Active immunity is so named because the host plays an active role in responding to the foreign antigen. The best example of active immunity is immunization, whereby a vaccine containing a foreign antigen is administered to a nonimmune host, resulting in active production of specific antibody and lymphocyte-based memory.
Passive immunity refers to transfer of soluble factors (either antibodies or cells) from an immune individual to a nonimmune host. This process confers immunity passively, without the recipient needing prior exposure to the antigen. A good example of passive immunity is parenteral administration of immune serum globulin to travelers as preexposure prophylaxis against unusual infections.
Innate Immune System
The innate immune system is phylogenetically older than the acquired (specific/adaptive) immune system.Latter might take 3-5 days to be effective. Therefore, there needs to be a system capable of controlling a pathogen during that time so it doesn’t damage the host.
Innate immune system is activated immediately and can rapidly control the replication of the infecting pathogens until the lymphocytes can deal with it. Innate immune system can interact with and control the adaptive immune responses.
The strategy of the IIS is to recognize a few highly conserved structures present in large groups of organisms. These structures are called pathogen-associated molecular patterns (PAMP), and the receptors of the IIS that recognize them are called pattern-recognition receptors PAMPs are produced only by microbial pathogens that may include bacterial lipopolysaccharides, peptidoglycan, mannas, and bacterial DNA/RNA. Read more
Overview of The Immune System
There are two broad categories of immunity involved in host defense – natural or innate and acquired. While natural immunity is more generalized, acquired immunity is more specific and adaptive. There are various levels of host defense that protect human body from invading attacks.
These are Read more
What Is Bone?
Bone is a mineralized connective tissue.
It is comprised of two subtypes: cortical or compact bone and cancellous or trabecular bone.
Cortical bone comprises 80 percent of the skeleton and is increased in long bone shafts.
Cancellous bone is in contact with bone marrow cells and is enriched in the vertebral bodies, pelvis, and proximal ends of femora, all of which are subject to osteoporosis and fractures.
Bone is comprised mainly of type I collagen and contain three cells types:
Osteoclasts, which resorb mineralized bone
osteoblasts, which synthesize the proteins of the bone matrix
Osteocytes which are probably osteoblasts that have secreted bone matrix and become buried within it.
Osteocytes communicate with each other through a canalicular system.
The skeleton contain 99 percent of the total body calcium, 80-85 percent of the phosphorus, and 66 percent of the magnesium.
Swine Flu Can Infect 40 percent of US
There is a disturbing news about Swineflu. CDC has estimated that it might affect up to 40 percent of Americans this year and next. Several hundred thousandsare expected to die vaccine campaign and other measures.
Swine flu has already has killed about 300 Americans and sickened more than 1 million, comparable to a seasonal flu .
Flu cases may explode in the fall, when schools open and become germ factories, and the new estimates dramatize the need to have vaccines and other measures in place. Read more
What Are Types of Joints In Human Body
Synarthrosis
Suture lines of the skull where adjoining cranial plates are separated by thin fibrous tissue.
Amphiarthroses
Adjacent bones are bound by flexible fibrocartilage that permits limited motion to occur.
For example the pubic symphysis, part of the sacroiliac joint, and intervertebral discs.
Diarthroses
These are the most common and most mobile joints. All have a synovial lining. They are subclassified into ball and socket (hip), hinge (interphalangeal), saddle (first carpometacarpal), and plane (patellofemoral) joints.
Musculoskeletal System – The Skeletal Muscles
There are approximately 640 muscles in human body and muscles constitute up to 40 percent of the adult body mass.
Skeletal muscle consists of cells called fibers. Fibers are grouped into fascicles.
Skeletal fibers are part of motor unit. Motor unit consists of a lower motor neuron originating from a spinal cord anterior horn cell and all the muscle fibers it innervates. All muscle fibers within a motor unit are of the same type. Different fibers within a single fascicle are innervated by different motor neurons. Read more
RANKL – Receptor Activator of NF-κ B ligand
RANKL (receptor activator of NF-κ B ligand) is a member of the tumor necrosis factor (TNF) superfamily. It is also called also known as TNF-related activation-induced cytokine (TRANCE), osteoprotegerin ligand (OPGL), and ODF (osteoclast differentiation factor).
RANKL is a cell membrane-bound ligand on osteoblasts and activated T cells. It binds RANK on osteblasts precursors, which causes the osteoblast to differentiate and become activated. Osteoprotegrin (OPG) is a soluble, secreted member of the TNF receptor family that competitively binds RANKL and prevents its binding to RANK, thus inhibiting osteoclastogenesis.
Expression of RANKL on osteoblasts is stimulated through
- Vitamin D receptor (1,25 OH vitamin D3)
- Protein kinase A (PGE2, parathyroid hormone)
- gp 130 (IL-11)
The periarticular osteoporosis seen on radiographs of individuals with inflammatory arthritis may be through local production of PGE2 and interleukins (TNFα, Il-1), causing up regulation of RANKL on osteoblasts and T cells leading to osteoclast activation.
Muscle Contraction and Relaxation
There are three types of muscle fibers.
Type 1 are slow twitch, oxidative fibers or red fibers. They respond to electrical stimuli slowly. They can resist fatigue with repeated stimulation. They possess many mitochondria and have a higher lipid content. Endurance training enhances metabolism of these fibers.
Type 2a are fast twitch, oxidative-glycolytic fibers and have inttermediate properties between type 1 and type 2b.
Type 2b are fast twitch, glycolytic fibers. they are also called white fibers. They respond rapidly and with greater force of contraction but also fatigue rapidly. These fibers contain more glycogen and have higher myophosphorylase and myoadenylate deaminase activity.
Strength training like weight lifting, sprinters, jumpers lead to hypertrophy of these fibers.
Muscle contraction
Muscle contraction occurs by shortening of myofilaments within muscle fibers. Stimulation causes an action potential to be transmitted along the sarcolemma, then through the T-tubule system to the sarcoplasmic reticulum. This causes release of calcium into the sarcoplasm.
As the calcium concentration increases, actin is released from a state of inhibition, allowing actin-myosin cross-linkage and shortening of the myofilaments. The muscle fiber shortens until calcium is actively pumped back into the sarcoplasmic reticulum, which breaks the cross-links to normal fiber contraction and relaxation.