References

Ammerman JW, Fuhrman JA, Hagstrom A, Azam F (1984) Bacterioplankton growth in seawater. 1. Growth kinetics and cellular characteristics in seawater cultures. Mar Ecol Prog Ser 18 31-39 Arai M, Suzuki-Koike M, Ohtake S, Ohba H, Tanaka K, Chiba J (2001) Common cell-surface antigens functioning in self-recognition reactions by both somatic cells and gametes in the solitary ascidian Halocynthia roretzi. Microbiol Immunol 45 857-866 Azumi K, Yokosawa H, Ishi S (1990a) Haolcyamines novel...

The Lectin Pathway

The best characterised recognition protein of the lectin pathway is mannan-binding lectin (MBL Petersen et al. 2001). MBL resembles C1q in that it contains globular heads and triple-helical collagen-like regions (Fig. 1). Its globular heads consist of C-type lectin domains, which bind to neutral sugars such as mannose, N-acetylglu-cosamine and fucose, in a calcium ion-dependent manner. MBL interacts with any of three serine proteases, called MBL-associated serine proteases (MASPs 1, 2, 3)....

Interactions Between Cellular and Humoral Immune Responses

Although the Drosophila cellular and humoral immune responses were originally believed to be largely independent (Braun et al. 1998), it appears that there may be a complex and as yet poorly defined relationship between the two processes. Studies of the Drosophila immune response in which flies are naturally infected by allowing microbes to enter the host via the digestive tract led to a number of insights into how hemocytes contribute to the initiation of the humoral response. It has been...

Conclusion

The complexity of host defenses and recognition strategies in urochordates represents intricate processes that provide the backdrop for both the innate and adaptive immune systems of species that appeared much later. Understanding the strategies employed by our ancestors will undoubtedly provide novel insights leading to new approaches to modulate immune function in plants and animals. Acknowledgements We are grateful to the Biological Station at Helgoland for supplying us with Ciona...

Others

The 52-amino-acid peptide adrenomedullin is involved in numerous physiological functions, including vasodilation, renal homeostasis, hormone regulation, neurotransmission and growth modulation (Zudaire et al. 2003). Adrenomedullin is expressed by many epithelia, including normal and neoplastic skin, in cells of the eccrine and apocrine sweat glands as well as in the sebaceous glands (Martinez et al. 1997). Adrenomedullin exhibits high antimicrobial activity against E. coli and moderate activity...

Nbs Lrr and TIR Domains of Defense

Perhaps among the most exciting discoveries in the biology of host immunity is that plant R proteins possess domains that share homology to animal proteins involved in innate immunity and or apoptosis (Hammond-Kosack and Jones 1997 Dangl and Jones 2001 Ausubel 2005). First, the TIR domain in the TIR-NBS-LRR R proteins shows homology to the Toll and IL-1 receptor. TIR domain-containing animal proteins such as Drosophila Toll and mammalian Toll-like receptors (such as TLR2, 4, 5, 9) are involved...

Receptors with Scavenger Like Activity Recognize a Variety of Microbes

PGRPs allow for specific recognition of Gram-positive versus Gram-negative bacteria and are important for activating both cellular and humoral immune resopo-nses. The first Drosophila PRR shown to trigger phagocytosis was the scavenger-receptor protein, dSR-CI. Chinese hamster ovary cells transfected with dSR-CI gained the ability to bind both E. coli and S. aureus, and the RNAi of dSR-CI in S2 cells decreased cell association with bacteria by 25 (Ramet et al. 2001). The predicted dSR-CI...

Complement Receptors

When C1q, MBL or the ficolins bind to targets they themselves act as opsonins and, in addition, they trigger complement activation resulting in the deposition of C3b, also an opsonin. Most molecules of C3b deposited on targets are gradually broken down (over a time-course of minutes to hours) to iC3b, a more effective opsonin. Eventually target-bound iC3b is more slowly degraded by proteases to a fragment called C3dg, which acts as an adjuvant. To interact with cells, these molecules require...

Adhesion Requires Integrins Rac and

At 16-24 h after egg deposition, plasmatocytes surround the parasite egg and spread. At 24 h after egg deposition, large numbers of lamellocytes are observed around the partially encapsulated egg. Extreme flattening is observed as the cells spread to form the outer layers in encapsulation (Russo et al. 1996). The mechanisms of this process involve integrins and the downstream small GTPases Rac and Rho, but may also involve other adhesion receptors and their downstream components. In mammals,...

An Infectious Disease and Innate Immunity Model

Recently, the zebrafish was established as a model for infection and immunity (Davis et al. 2002 Menudier et al. 1996 Neely et al. 2002 Phelan et al. 2005b Pressley et al. 2005 Prouty et al. 2003 van der Sar et al. 2003, 2006). The zebrafish is particularly useful because each point in its development can be easily exploited to learn important information about the immune system. During the first four days of development, the zebrafish exhibits no adaptive immunity markers (Traver et al. 2003)....

Role of TIRContaining Adapter Molecules in TLR Signaling

Five TIR-containing intracellular adapter molecules have been identified, and four are known to participate in TLR signaling. MyD88 was the first adapter protein found to mediate IL-1R and TLR signaling (Muzio et al. 1997 Wesche et al. 1997 Burns et al. 1998 Kawai et al. 1999, 2001). MyD88 is comprised of a C-terminal TIR domain involved in interaction with TLRs and an N-terminal death domain that associates with IRAK family members (Muzio et al. 1997 Wesche et al. 1997 Burns et al. 1998)....

Natural History and Ecology of Urochordates

History Ecology

Urochordates are exclusively marine animals, occurring worldwide in all oceans. The environmental variables most important in determining their distribution are temperature, salinity, light, and hydrodynamics (Lambert 2005). In their dimorphic life cycle, a non-feeding, short-living pelagic larva is followed by the sessile filterfeeding adult ascidian (see Fig. 2). The efficient filtration abilities may be the key to recent population explosions of various urochordate species in regions close...

TLRs as Primary Sensors of Pathogenic PAMPS and Endogenous Danger Molecules

TLRs are evolutionary conserved, non-clonally distributed, type I signaling receptors comprised of an ectodomain with leucine-rich repeats, a single transmembrane region, and a cytoplasmic tail that contains a conserved signaling TIR domain (Martin and Wesche 2002 Underhill and Ozinski 2002 Kaisho and Akira 2006). TLRs are expressed on epithelial and endothelial cells, monocytes, macrophages, neutrophils, dendritic cells, and lymphocytes (Zarember and Godowski 2002 Iwasaki and Medzhitov 2005...

Antimicrobial Peptides and Diseases 51 Skin Diseases

The identification of various antimicrobial peptides from lesional skin of patients with the common chronic inflammatory skin disease psoriasis might explain the phenomenon that these patients suffer from significantly fewer skin infections than expected (Henseler and Christophers 1995). Psoriatic scale extracts are known to contain a broad spectrum of antimicrobial peptides when compared with healthy stratum corneum proteins (Harder and Schr der 2005) and several of these proteins, like hBD-2...

Innate Immune System of the Zebrafish Danio rerio

2 Components of Innate 2.1 General 2.2 Drosophila Toll Identification and Recognition of a Dually Functioning 2.3 TLRs and TIR-Bearing Adaptor 3 Zebrafish as a Model for Infectious Disease and Innate Immune 3.2 Forward and Reverse 3.3 An Infectious Disease and Innate Immunity 4 NK-Like 5 Additional Innate Immunity Receptors in Zebrafish 6 Zebrafish Phagocytes 7 Conclusion References Abstract There has been a revolution in immunology in recent years that has transformed the paradigmatic...

Balancing Selection Results from Indirect Recognition

R proteins that are engaged in indirect recognition of Avr proteins are predicted to function in protein complexes as guards of virulence targets of the pathogen Avr proteins. Compared with direct detection of pathogens via structural R-Avr recognition, it is conceivable that there may be selective advantages for indirect detection by monitoring the virulence function of Avr proteins, because structural modification of an Avr protein by mutations cannot escape R recognition unless the virulence...

The IMD Pathway

The IMD pathway is potently activated by DAP-type PGN derived from Gramnegative bacteria and certain Gram-positive bacteria, such as Bacillus spp. Initially, it was believed that LPS activated the IMD pathway Silverman et al. 2000 Werner et al. 2003 . However, this did not account for the activation of the IMD pathway by certain Gram-positive bacteria Kaneko et al. 2004 Lemaitre et al. 1997 Leulier et al. 2003 . Subsequently, it was demonstrated that the commercial LPS preparations often used...

Phagocytosis Requires Reorganization of the Actin Cytoskeleton

As in other animal cells, phagocytosis in plasmatocytes begins by the extension of actin-rich pseudopodia that surround and engulf the targeted microbe. This phenomenon has been observed in vitro in the S2 and mbn-2 cell lines Pearson et al. 2003 Johansson et al. 2005 Stroschein-Stevenson et al. 2006 . The formation of pseudopodia is dependent on remodeling the cytoskeleton through extensive actin polymerization and depolymerization, and this process is extremely well characterized. The process...

Cellular Immune Responses in Drosophila melanogaster

Adrienne Ivory, Katherine Randle, and Louisa Wu 2.1 Recognition Centers on Membrane 2.2 Lamellocyte Proliferation Necessary for Successful Encapsulation Response 78 2.3 Adhesion Requires Integrins, Rac, and 2.4 Encapsulation Terminates with the Formation of Basement Membrane 82 3.1 Proteins Opsonize Invading Bacteria and Fungi to Promote Phagocytosis 84 3.2 Transmembrane and Circulating Peptidoglycan Recognition Proteins are Involved in the Recognition of 3.3 Receptors with Scavenger-Like...

Classical Pathway

The mechanisms of action and activation of complement have been extensively reviewed McAleer and Sim 1993 Law and Reid 1995 Walport 2001a, b Sim and Tsiftsoglou 2004 . The proteins involved in the classical pathway of complement include C1q, C1r, C1s, and C2-C9 Fig 2 . One molecule of C1q associates with 1 C1r2s2 heterotetramer in the presence of Ca2 Fig 1 The protein complex is called C1. The classical pathway is activated by the binding of C1q in the C1 complex to the activator. C1q binds via...

Indirect RAvr Interaction the Guard Hypothesis

However, the majority of the available R-Avr pairs failed to show any physical interaction despite repeated experiments. This, together with the reasoning that, even though R genes are abundant in plants, there are still far fewer R genes in plant genomes than potential genes encoding effector proteins in pathogens, led to the indirect recognition model, i.e. the guard hypothesis Van der Biezen and Jones 1998a Dangl and Jones 2001 . This model assumes that Avr proteins are pathogen effectors...