Ticks transmit more different kinds of pathogenic organisms than any other hematophagous arthropod. This paper attempts to review the literature available on the cell-mediated and humoral responses of ticks. The cell-mediated defense responses by invertebrates are simpler than vertebrates, but are effective as a second line of defense against invasion by microorganisms. Hemocytes play a major role in this immune response through phagocytosis, nodule formation and encapsulation of invading foreign materials. These mechanisms appear to function in both soft and hard ticks. Humoral immune responses consist of three main types; humoral encapsulation, hemagglutination and production of antimicrobial proteins. Humoral encapsulation is elicited by the prophenoloxidase activating system and has only been shown to function in the soft tick Ornithodoros moubata. However, recent studies show the hard ticks also have prophenoloxidase activating cofactors indicating humoral encapsulation also functions in these ticks. Tick lectins function in hemagglutination of various microorganisms in both soft and hard ticks and also appear to function as recognition molecules of nonself and possibly in the transmission of pathogenic microorganisms. Ticks also have numerous antimicrobial proteins that can attack the invading microorganisms. Lysozymes have been shown to have bactericidal effects in several tick species and work in concert with other antimicrobial peptides to kill invaders. Cystatins, classic cysteine protease inhibitors, have recently been shown to function in innate immune responses of ticks. Hemoglobin fragments have antimicrobial activity in the midgut of ticks. Defensins show expression up-regulated by blood feeding and are effective antimicrobial agents with some differences between soft and hard ticks. Other novel antimicrobial peptides have been isolated from various species of soft and hard ticks, but their functions remain to be elucidated. Understanding these innate immune mechanisms in ticks is essential to develop strategies for reducing the transmission of diseases to man and animals.

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Pelzneria uncinata, a new species of Histiostomatidae (Acari, Astigmata) is described from Japan, South Korea, Russian Far East and Tibet based on deutonymphs phoretic on adult Nicrophorus concolor Kraatz (Coleoptera, Silphidae). This species is mostly found on the hind wings and underside of elytra of the host beetles and readily distinguished from the known members of the genus by the following characteristics: 1) prodorsum with anterior margin well sclerotized, 2) among the dorsal hysterosomal setae, d₁, e₁ and h₁ much longer than the others and provided with a few minute barbs distally, 3) seta w on tarsus III small, not longer than tarsal width at its insertion.

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