7. Cytological characteristics of haematological cells from Australian mammals All Australian mammals possess erythrocytes, leukocytes and platelets. The general characteristics of these cells have been described in the relevant chapters preceding this one. The morphological characteristics may vary between species and these differences are described in this chapter. The characteristics of erythrocytes, such as the degree of anisocytosis, the proportion of polychromatophilic erythrocytes and ‘variant’ erythrocytes (see Chapter 2) and the presence of rouleaux, may differ between species, but it is typically the leukocytes that show the most striking variation between species, with differences in the number and proportion of each type of leukocyte as well as in the morphological appearance of each type of cell. Most notably, the granulocytes vary in the size, shape, number, density and hue of the cytoplasmic granules that define them. Platelets typically have the least variation between species, but may exhibit subtle differences in the colour of the cytoplasm and the prominence of cytoplasmic granules. In most haematological assessments, the accurate identification of the cells present (particularly leukocytes) is crucial, but can be very difficult for inexperienced haematologists or for species that are not commonly examined by experienced haematologists. The following text comprises descriptions of the haematological cells from a broad range of Australian mammals that are intended to provide a reference for the light microscopic appearance of these cells. Corresponding photographs can be found in Plates 73–456. It was not feasible to document the haematological cells from every species of Australian mammal; however, I have endeavoured to include representative species. In addition, the characteristics of haematological cells from some non-Australian species have also been considered, usually a closely related species to those found in Australia (such as tree-kangaroos from New Guinea) and these have been indicated by a dagger symbol (†). This chapter is not intended to be read from start to finish, but rather for the reader to look up descriptions of cells from animals of interest as the need arises. In some species, samples of blood from only a few individuals were available for assessment, which did not allow all the expected haematological cell types to be recognised. In certain species, some of the leukocytes are infrequently observed and many slides must be examined before they are found. Consequently, many samples must be exhaustively examined before deciding that a certain type of leukocyte is absent in a nominated species. The blood films that were examined for the compilation of this chapter were obtained from many sources and consequently were produced and processed by different methods, notably using different stains, including May, Grunwald and Giemsa stains, Wright’s stain, Wright’s and Giemsa stains, Leishman’s stain and DiffQuik® stain (see Appendix 3). Therefore, the tinctorial characteristics of the cells presented here as examples will have been affected by many factors, including the type of stain and staining method (manual staining methods are more variable than automated methods), fixation and the time elapsed before staining, as well as photographic factors. Consequently, the reader will need to take into account that the colours of cells in any given processed blood film will look different to those published here. (Plates 73–76) The erythrocytes of the platypus are eosinophilic and have either no central pallor or only a small amount, indicating little concavity in the cells. Minimal anisocytosis or polychromasia is evident in samples from clinically healthy animals. Neutrophils have a nucleus with 1-5 lobes composed of coarsely clumped chromatin and a moderate amount of cytoplasm that may have a slight granular appearance because of staining of secondary granules. Stages of neutrophil development with a non-segmented nucleus (i.e. myelocytes and metamyelocytes) are found in the peripheral blood of clinically healthy animals. Döhle bodies may also be observed within neutrophils from healthy animals. Lymphocytes are typically small to medium-sized cells with a round to ovoid nucleus composed of dense, coarsely clumped chromatin and a small rim of basophilic cytoplasm. Occasional cells with a reniform or irregularly shaped nucleus may be observed. Monocytes have a horse-shoe shaped nucleus composed of coarsely clumped chromatin and a moderate amount of basophilic granular cytoplasm, which may also contain small azurophilic (primary) granules. Eosinophils have an ovoid (non-segmented) to tri-lobed nucleus composed of coarsely clumped chromatin. Eosinophil cytoplasm contains many small, round, eosinophilic granules that are ‘evenly’ distributed throughout the cytoplasm. Basophils were not recognised in the blood films examined. (Plates 77–79) The erythrocytes of the short-beaked echidna are eosinophilic discocytes with a variable amount of central pallor (none to moderate). Minimal anisocytosis and occasional polychromatophilic erythrocytes are noted in samples from clinically healthy animals. Neutrophils have a nucleus with 3–7 lobes and often it has a tortuous appearance. The cytoplasm of the neutrophils is often pale grey because of the fine granulation. Lymphocytes are generally small to medium-sized cells, with a nucleus of dense, coarsely clumped chromatin and a small rim of strongly basophilic cytoplasm that is often quite granular in appearance. Monocytes have an ovoid to irregular nucleus composed of fine to reticular chromatin. The cytoplasm is basophilic with a fine granularity and may contain multiple vacuoles. Eosinophils are characterised by many short, rod-shaped, brightly eosinophilic granules that are present at high density throughout the cytoplasm. The nucleus has 2–3 lobes and fine to coarse chromatin, and is often partially obscured by the number and density of the granules. The basophils of the short-beaked echidna are characterised by a nucleus with 3–4 lobes composed of coarsely clumped chromatin and cytoplasm that contains few to moderate numbers of unevenly distributed basophilic granules. The density of the granules is sparse to moderate and it is possible to observe the basophilic cytoplasm between the granules. (Plates 80–82) The erythrocytes of the long-beaked echidna are eosinophilic discocytes with a variable amount of central pallor. Mild anisocytosis may be evident in samples from clinically healthy animals. Neutrophils have a nucleus with 3–7 lobes and it may be quite tortuous in appearance. The cytoplasm of neutrophils usually stains neutral. Occasional cells may contain Döhle bodies. The predominant lymphocyte is a small cell with a round nucleus and a small rim of basophilic cytoplasm that may be difficult to observe in some cases. Occasional cells have an indented nucleus. Larger lymphocytes have a pleomorphic appearance with an irregular nucleus, less dense chromatin and small to moderate amounts of basophilic cytoplasm that may be unevenly distributed around the cell. Monocytes have an indented or horse-shoe shaped nucleus that is composed of reticular chromatin and moderate amounts of granular basophilic cytoplasm. Eosinophils typically have a nucleus with 2–3 lobes composed of reticular to coarsely clumped chromatin. The cytoplasm contains many round, brightly eosinophilic granules. Basophils were not recognised in the limited number of blood films examined. (Plates 83–86) The erythrocytes of the eastern grey kangaroo are eosinophilic discocytes with prominent central pallor. Mild anisocytosis and rouleaux may be present in clinically healthy individuals. Neutrophils have 3–7 nuclear lobes composed of closely clumped chromatin and cytoplasm that is usually colourless but may exhibit small amphophilic granules that represent the secondary granules. Lymphocytes have a pleomorphic appearance. Small lymphocytes have a nucleus composed of dense, coarsely clumped chromatin with a small amount of basophilic cytoplasm. Larger lymphocytes have a less dense chromatin and larger amounts of less basophilic cytoplasm. Occasional lymphocytes may have a reniform nucleus. Monocytes have an irregular nucleus composed of coarse reticular chromatin and basophilic cytoplasm. Vacuoles are generally not a feature of the cytoplasm, but occur occasionally. Eosinophils have 2–4 nuclear lobes composed of coarse chromatin. The cytoplasm contains many ovoid, eosinophilic granules that are distributed ‘evenly’ at moderate density throughout. The colour of these granules may vary from brightly eosinophilic to a pale brown, depending on which stain is used. Basophils have a high density of round, strongly basophilic granules in the cytoplasm, which typically obscure nuclear detail. (Plates 87–90) The erythrocytes of the western grey kangaroo are eosinophilic discocytes with central pallor. Mild anisocytosis and rouleaux may be present in clinically healthy individuals. Neutrophils have 3–7 nuclear lobes composed of densely clumped chromatin and cytoplasm that is usually colourless but may be finely granular (amphophilic) because of staining of the secondary granules. Lymphocyte morphology varies from small to large lymphocytes in varying proportions between animals. Small lymphocytes have a nucleus composed of dense chromatin and a small amount of basophilic cytoplasm. The larger lymphocytes have less dense chromatin and larger amounts of less basophilic cytoplasm. Occasional lymphocytes may have a reniform nucleus. Monocytes have a nucleus composed of coarse reticular chromatin and generally basophilic cytoplasm (which may contain vacuoles). Eosinophils have 2–4 nuclear lobes composed of coarse chromatin. The cytoplasm contains many ovoid, regular eosinophilic granules that are evenly distributed throughout the cytoplasm at a moderate density. Basophils have a high density of round, strongly basophilic granules in the cytoplasm, which typically obscure the nucleus. (Plates 91–94) The erythrocytes of the red kangaroo are eosinophilic discocytes with moderate to prominent central pallor. Mild anisocytosis, rouleaux, occasional Howell-Jolly bodies and polychromatophilic erythrocytes are found in samples from clinically healthy animals. Neutrophils have 3–7 nuclear lobes composed of coarsely clumped chromatin and often there are fine strands of chromatin separating the nuclear lobes. The cytoplasm is colourless and may be finely granular. Most lymphocytes are small to medium-sized cells, with moderately dense chromatin and a small rim of basophilic cytoplasm. Monocytes have an indented to irregular nucleus composed of reticular to coarse chromatin and a moderate amount of basophilic cytoplasm, which often contains one to several clear vacuoles. Eosinophils typically have a bi-lobed nucleus composed of reticular to coarse chromatin and cytoplasm that contains a high density of round, brightly eosinophilic secondary granules. Basophils have a segmented nucleus and cytoplasm that contains a high density of round, strongly basophilic granules. (Plates 95–97) (Plates 98–100) Erythrocytes of the red-necked wallaby are eosinophilic discocytes with distinct central pallor. Rouleaux and occasional polychromatophilic erythrocytes may be evident in clinically healthy individuals. Neutrophils have a nucleus with 3–6 nuclear lobes, often with a tortuous morphology, and typically pale cytoplasm. Lymphocyte morphology is variable with small, medium and large lymphocytes observed. Small lymphocytes typically have a round nucleus composed of dense, coarsely clumped chromatin and a small rim of basophilic cytoplasm. In comparison, larger lymphocytes have less dense chromatin and a larger amount of cytoplasm. Occasional ‘reactive’ lymphocytes, characterised by either increased basophilia in the cytoplasm or the presence of a nucleolus, may be observed. Monocytes have an irregularly shaped nucleus that is composed of reticular to coarse chromatin and a moderate to large amount of a granular, basophilic cytoplasm. Eosinophils have 2–4 nuclear lobes composed of coarsely clumped chromatin. The cytoplasm, when apparent, is a pale basophilic colour and contains brightly eosinophilic, round to ovoid secondary granules distributed at a high density throughout the cytoplasm. Basophils are rarely observed and are characterised by cytoplasm that contains a high density of small, round, deeply basophilic granules, which may obscure the nucleus. (Plates 101–104) The erythrocytes of the black-striped wallaby are eosinophilic discocytes with moderate central pallor. Neutrophils have a nucleus with 3–7 lobes composed of coarsely clumped chromatin and neutral staining cytoplasm. Lymphocytes are typically small to mediumsized cells with a round nucleus composed of coarsely clumped, dense chromatin and a small amount of granular, basophilic cytoplasm. Monocytes typically have an irregularly shaped nucleus composed of reticular to coarse chromatin and a small to moderate amount of granular, basophilic cytoplasm. Eosinophils typically have a bi-lobed nucleus composed of coarsely clumped chromatin. The cytoplasm contains many ovoid, eosinophilic granules. Basophils have not been observed in the small number of samples examined. (Plates 105–108) The erythrocytes of Parma wallabies are typically eosinophilic discocytes with prominent central pallor. Rouleaux may be present in samples from clinically healthy animals and occasional Howell-Jolly bodies, polychromatophilic erythrocytes and mild anisocytosis may also be noted. Neutrophils have a nucleus with 3–6 nuclear lobes composed of coarsely clumped chromatin and cytoplasm with no apparent granules. Small, medium and large lymphocytes may all be present, with medium-and large-sized lymphocytes more commonly observed than small lymphocytes. Small lymphocytes have a round nucleus composed of dense, coarsely clumped chromatin and a small rim of basophilic cytoplasm. In comparison, larger lymphocytes have less dense chromatin and a larger amount of cytoplasm. Monocytes are the largest leukocyte present and have an indented or irregularly shaped nucleus composed of reticular chromatin and a moderate amount of finely granular, grey to basophilic cytoplasm. Eosinophils have a nucleus with 2–4 lobes composed of coarsely clumped chromatin. Eosinophil cytoplasm is neutral to slightly basophilic and contains many round to ovoid, eosinophilic secondary granules that are densely but irregularly distributed throughout the cytoplasm, yet usually do not obscure nuclear detail. Occasional larger prominent granules are evident among the background of more uniform granules. Basophils were not recognised in the samples examined. MONOTREMES Plate 73 Three neutrophils from the blood of a platypus (MGG stain). Plate 74 Eosinophil, two small lymphocytes and a myelocyte of neutrophil lineage (arrow) from the blood of a platypus (MGG stain). Plate 75 Monocyte and neutrophil from the blood of a platypus (MGG stain). Plate 76 Monocyte and myelocyte of eosinophil lineage (arrow) from the blood of a platypus. The latter has an irregular cell outline because of distortion by the surrounding cells and drying. (MGG stain.) Plate 77 Two neutrophils and a lymphocyte from the blood of a short-beaked echidna (WG stain). Plate 78 Eosinophil from the blood of a short-beaked echidna (WG stain). Plate 79 Monocyte and lymphocyte from the blood of a short-beaked echidna (WG stain). Plate 80 Neutrophil and lymphocyte from the blood of a long-beaked echidna† (MGG stain). Plate 81 Eosinophil and lymphocyte from the blood of a long-beaked echidna† (MGG stain). Plate 82 Neutrophil and monocyte from the blood of a long-beaked echidna† (MGG stain). KANGAROOS AND WALLABIES Plate 83 Neutrophil from the blood of an eastern grey kangaroo. A refractile artefact caused by incomplete drying of the slide prior to staining is evident on the erythrocytes. (WG stain.) Plate 84 Eosinophil from the blood of an eastern grey kangaroo (WG stain). Plate 85 A typical small lymphocyte, a lymphocyte with an indented nucleus and a monocyte from the blood of an eastern grey kangaroo. The monocyte illustrates a commonly encountered characteristic whereby cell shape is mildly distorted by the surrounding cells, in this case, erythrocytes (MGG stain). Plate 86 Basophil from the blood of an eastern grey kangaroo (WG stain). Plate 87 Neutrophil from the blood of a western grey kangaroo. An artefactual vacuole is present in the cytoplasm. (WG stain.) Plate 88 Eosinophil from the blood of a western grey kangaroo (WG stain). Plate 89 Basophil from the blood of a western grey kangaroo (WG stain). Plate 90 Monocyte and lymphocyte from the blood of a western grey kangaroo (WG stain). Plate 91 Neutrophil and lymphocyte from the blood of a red kangaroo (WG stain). Plate 92 Eosinophil from the blood of a red kangaroo (WG stain). Plate 93 Monocyte and metarubricyte from the blood of a red kangaroo (WG stain). Plate 94 A mildly damaged basophil from the blood of a red kangaroo, in which the individual secondary granules can be seen in the cytoplasm (WG stain). Plate 95 Neutrophil, eosinophil and lymphocyte from the blood of a swamp wallaby (MGG stain). Plate 96 Eosinophil and lymphocyte from the blood of a swamp wallaby (MGG stain). Plate 97 Monocyte from the blood of a swamp wallaby (MGG stain). Plate 98 Two neutrophils, a monocyte and a lymphocyte from the blood of a red-necked wallaby (MGG stain). Plate 99 Eosinophil from the blood of a rednecked wallaby. Traditional 35-mm photography typically results in a more brownish appearance of eosinophil granules in the photomicrograph than is directly observed in the blood film. (MGG stain.) Plate 100 Basophil from the blood of a red-necked wallaby (MGG stain). Plate 101 Neutrophil from the blood of a black-striped wallaby (DQ stain). Plate 102 Eosinophil from the blood of a black-striped wallaby (DQ stain). Plate 103 Lymphocyte from the blood of a black-striped wallaby (DQ stain). Plate 104 Monocyte from the blood of a black-striped wallaby (DQ stain). Plate 105 Neutrophil from the blood of a Parma wallaby. There is also a Howell-Jolly body (arrow). (MGG stain.) Plate 106 Eosinophil from the blood of a Parma wallaby (MGG stain). Plate 107 Lymphocyte from the blood of a Parma wallaby (MGG stain). Plate 108 Monocyte from the blood of a Parma wallaby (MGG stain). Plate 109 Neutrophil and lymphocyte from the blood of a Tammar wallaby (WG stain). Plate 110 Eosinophil from the blood of a Tammar wallaby (WG stain). Plate 111 Monocyte and lymphocyte from the blood of a Tammar wallaby (WG stain). Plate 112 Neutrophil from the blood of an agile wallaby (MGG stain). Plate 113 Eosinophil from the blood of an agile wallaby (MGG stain). Plate 114 Lymphocyte from the blood of an agile wallaby (MGG stain). Plate 115 Monocyte from the blood of an agile wallaby (MGG stain). Plate 116 Two neutrophils from the blood of a Goodfellow’s tree-kangaroo† (MGG stain). Plate 117 Eosinophil from the blood of a Goodfellow’s tree-kangaroo† (MGG stain). Plate 118 Two lymphocytes, one with an indented nucleus, from the blood of a Goodfellow’s tree-kangaroo† (MGG stain). Plate 119 Monocyte from the blood of a Goodfellow’s tree-kangaroo† (MGG stain). Plate 120 Basophil from the blood of a Goodfellow’s tree-kangaroo†. The cell is in a region of the blood film that prevents it from adequately spreading out, which combined with the density of secondary granules gives the cell an overall dark appearance and obscures the nuclear detail. (MGG stain.) Plate 121 Two neutrophils, an eosinophil and a small, pale clump of platelets (arrow) from the blood of a Matschie’s tree-kangaroo† (WG stain). Plate 122 Lymphocyte from the blood of a Matschie’s tree-kangaroo† (WG stain). Plate 123 Monocyte from the blood of a Matschie’s tree-kangaroo† (WG stain). Plate 124 Basophil from the blood of a Matschie’s tree-kangaroo† (WG stain). Plate 125 Neutrophil from the blood of a Lumholtz’s tree-kangaroo (MGG stain). Plate 126 Eosinophil from the blood of a Lumholtz’s tree-kangaroo and a platelet clump (arrow) (MGG stain). Plate 127 Two lymphocytes from the blood of a Lumholtz’s tree-kangaroo (MGG stain). Plate 128 Monocyte from the blood of a Lumholtz’s tree-kangaroo. There is also a Howell-Jolly body (arrow). (MGG stain.) Plate 129 Basophil from the blood of a Lumholtz’s tree-kangaroo (MGG stain). Plate 130 Neutrophil, eosinophil and lymphocyte from the blood of a common wallaroo. The erythrocytes are exhibiting rouleaux (MGG stain). Plate 131 Neutrophil and lymphocyte from the blood of a common wallaroo (MGG stain). Plate 132 Monocyte from the blood of a common wallaroo (MGG stain). Plate 133 Eosinophil from the blood of a common wallaroo (MGG stain). Plate 134 Two neutrophils and an eosinophil from the blood of an antilopine wallaroo (WG stain). Plate 135 Eosinophil from the blood of an antilopine wallaroo (WG stain). Plate 136 Lymphocyte from the blood of an antilopine wallaroo (WG stain). Plate 137 Monocyte from the blood of an antilopine wallaroo (WG stain). Plate 138 Neutrophil and eosinophil from the blood of a black-footed rock-wallaby (WG stain). Plate 139 Lymphocyte from the blood of a black-footed rock-wallaby (WG stain). Plate 140 Monocyte from the blood of a black-footed rock-wallaby (WG stain). Plate 141 Basophil from the blood of a black-footed rock-wallaby has been distorted by the surrounding cells (WG stain). Plate 142 Neutrophil and eosinophil from the blood of a yellow-footed rock-wallaby (MGG stain). Plate 143 Lymphocyte from the blood of a yellow-footed rock-wallaby (MGG stain). Plate 144 Monocyte from the blood of a yellow-footed rock-wallaby (MGG stain). Plate 145 Basophil from the blood of a yellow-footed rock-wallaby (MGG stain). Plate 146 Two neutrophils and a lymphocyte (with several azurophilic granules evident in the cytoplasm) from the blood of a brush-tailed rock-wallaby (MGG stain). Plate 147 Eosinophil from the blood of a brush-tailed rock-wallaby (MGG stain). Plate 148 Two lymphocytes from the blood of a brush-tailed rock-wallaby (MGG stain). Plate 149 Monocyte from the blood of a brush-tailed rock-wallaby (MGG stain). Plate 150 Basophil from the blood of a brush-tailed rock-wallaby (MGG stain). Plate 151 Neutrophil and lymphocyte from the blood of an allied rock-wallaby (MGG stain). Plate 152 Lymphocyte from the blood of an allied rock-wallaby (MGG stain). Plate 153 Monocyte from the blood of an allied rock-wallaby (MGG stain). Plate 154 Eosinophil from the blood of an allied rock-wallaby (MGG stain). Plate 155 Basophil from the blood of an allied rock-wallaby (MGG stain). Plate 156 Two neutrophils and a basophil from the blood of a Proserpine rock-wallaby (MGG stain). Plate 157 Basophil from the blood of a Proserpine rock-wallaby showing greater density of granules than the basophil in Plate 156 (MGG stain). Plate 158 Eosinophil from the blood of a Proserpine rock-wallaby (MGG stain). Plate 159 Three lymphocytes from the blood of a Proserpine rock-wallaby. Note also the filamentous and disc-shaped platelets. (MGG stain.) Plate 160 Neutrophil and two monocytes from the blood of a Proserpine rock-wallaby (MGG stain). Plate 161 Neutrophil from the blood of a nabarlek (DQ stain). Plate 162 Lymphocyte from the blood of a nabarlek (DQ stain). Plate 163 Monocyte from the blood of a nabarlek (DQ stain). Plate 164 Neutrophil and lymphocyte from the blood of a whiptail wallaby (MGG stain). Plate 165 Eosinophil and lymphocyte from the blood of a whiptail wallaby (MGG stain). Plate 166 Monocyte from the blood of a whiptail wallaby (MGG stain). Plate 167 Neutrophil from the blood of a northern nailtail wallaby (MGG stain). Plate 168 Eosinophil from the blood of a northern nailtail wallaby (MGG stain). Plate 169 Lymphocyte from the blood of a northern nailtail wallaby (MGG stain). Plate 170 Monocyte from the blood of a northern nailtail wallaby (MGG stain). Plate 171 Basophil from the blood of a northern nailtail wallaby (MGG stain). Plate 172 Neutrophil and a monocyte with an annular nucleus from the blood of a bridled nailtail wallaby (MGG stain). Plate 173 Eosinophil from the blood of a bridled nailtail wallaby (MGG stain). Plate 174 Small lymphocyte and mildly lysed large lymphocyte from the blood of a bridled nailtail wallaby (MGG stain). Plate 175 Neutrophil from the blood of a quokka (WG stain). Plate 176 Eosinophil from the blood of a quokka (WG stain). Plate 177 Lymphocyte from the blood of a quokka. A lysed cell is also present. (WG stain.) Plate 178 Monocyte from the blood of a quokka (WG stain). Plate 179 Basophil from the blood of a quokka (WG stain). Plate 180 Neutrophil from the blood of a rufous bettong (DQ stain). Plate 181 Eosinophil from the blood of a rufous bettong (DQ stain). Plate 182
INTRODUCTION
MONOTREMES
Platypus
Short-beaked echidna
Long-beaked echidna†
KANGAROOS AND WALLABIES
Eastern grey kangaroo
Western grey kangaroo
Red kangaroo
Swamp wallaby
Red-necked wallaby
Black-striped wallaby
Parma wallaby
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